NAME
bgpd.conf
—
BGP routing daemon configuration
file
DESCRIPTION
The bgpd(8) daemon implements the Border Gateway Protocol version 4 as described in RFC 4271.
The bgpd.conf
config file is divided into
the following main sections:
- MACROS
- User-defined variables may be defined and used later, simplifying the configuration file.
- GLOBAL CONFIGURATION
- Global settings for bgpd(8).
- SET CONFIGURATION
- Various lookup tables are defined in this section.
- NETWORK AND FLOWSPEC ANNOUNCEMENTS
- Networks which should be announced by bgpd(8) are set in this section.
- MPLS VPN CONFIGURATION
- The definition and properties for BGP MPLS VPNs are set in this section.
- NEIGHBORS AND GROUPS
- bgpd(8) establishes sessions with neighbors. The neighbor definition and properties are set in this section, as well as grouping neighbors for the ease of configuration.
- FILTER
- Filter rules for incoming and outgoing UPDATES.
With the exception of macros, the sections should be grouped and
appear in bgpd.conf
in the order shown above.
The current line can be extended over multiple lines using a backslash (‘\’). Comments can be put anywhere in the file using a hash mark (‘#’), and extend to the end of the current line. Care should be taken when commenting out multi-line text: the comment is effective until the end of the entire block.
Argument names not beginning with a letter, digit, or underscore must be quoted.
Additional configuration files can be included with the
include
keyword, for example:
include "/etc/bgpd/bgpd-10.0.0.1.filter"
MACROS
Macros can be defined that will later be expanded in context.
Macro names must start with a letter, digit, or underscore, and may contain
any of those characters. Macro names may not be reserved words (for example,
AS
, neighbor
, or
group
). Macros are not expanded inside quotes.
For example:
peer1="1.2.3.4" neighbor $peer1 { remote-as 65001 }
GLOBAL CONFIGURATION
These settings affect the operation of the bgpd(8) daemon as a whole.
AS
as-number [as-number]- Set the local
autonomous
system number to as-number. A fallback
2-byte AS number may follow a 4-byte AS number for neighbors that do not
support 4-byte AS numbers. The standard and default fallback AS number is
23456.
The AS numbers are assigned by local RIRs, such as:
- AfriNIC
- for Africa
- APNIC
- for Asia Pacific
- ARIN
- for North America and parts of the Caribbean
- LACNIC
- for Latin America and the Caribbean
- RIPE NCC
- for Europe, the Middle East, and parts of Asia
The AS numbers 64512 – 65534 are designated for private use. The AS number 23456 is reserved and should not be used. 4-byte AS numbers may be specified in either the ASPLAIN format:
AS 196618
or in the older ASDOT format:
AS 3.10
connect-retry
seconds- Set the number of seconds to wait before attempting to re-open a connection. This timer should be sufficiently large in EBGP configurations. The default is 120 seconds.
dump
[rib
name] (table-v2
|table-mp
|table
) file [interval]dump
(all
|updates
) (in
|out
) file [interval]- Dump the RIB, a.k.a. the
routing
information base, or dump ongoing BGP activity, in Multi-threaded
Routing Toolkit (MRT) format. The file is subject to
strftime(3)-expansion.
The
table-v2
andtable-mp
RIB formats store multi-protocol RIBs correctly, but thetable
format does not. The latter two are provided only to support third-party tools lacking support for the recommendedtable-v2
format. Dump an alternative RIB by specifying name. Specify an interval in seconds for periodic RIB dumps.The following will dump the entire RIB table, at startup and every 5 minutes thereafter, to a new file:
dump table-v2 "/tmp/rib-dump-%H%M" 300
Dumps of ongoing BGP activity include all BGP state transitions, and all BGP messages in the specified direction. Use
updates
to dump only BGP UPDATE messages, without state transitions. Specify an interval in seconds to restart periodically with a new file:dump all in "/tmp/all-in-%H%M" 300
fib-priority
prio- Set the routing priority to prio. The default is 48.
fib-update
(yes
|no
)- If set to
no
, do not update the Forwarding Information Base, a.k.a. the kernel routing table. The default isyes
. holdtime
seconds- Set the announced holdtime in seconds. This is exchanged with a neighbor
upon connection establishment, in the OPEN message, and
the shortest holdtime governs the session.
The neighbor session is dropped if the session holdtime passes without receipt of a KEEPALIVE or an UPDATE message from the neighbor. The default is 90 seconds.
holdtime min
seconds- The minimum acceptable holdtime in seconds. This value must be at least 3.
listen on
address [port
port]- Specify the local IP address and optional port for bgpd(8) to listen on. The default is to listen on all local addresses on the current default routing domain.
log updates
- Log sent and received BGP update messages.
nexthop
qualify
via
(bgp
|default
)- If set to
bgp
, bgpd(8) may verify nexthops using BGP routes. If set todefault
, bgpd(8) may verify nexthops using the default route. By default bgpd(8) uses only static routes or routes added by other routing daemons, such as ospfd(8). rde
evaluate
(default
|all
)- If set to all, keep evaluating alternative paths in case the selected path is filtered out. By default if a path is filtered by the output filters then no alternative path is sent to this peer.
rde
med
compare
(always
|strict
)- If set to
always
, the MULTI_EXIT_DISC attributes will always be compared. The default isstrict
, where the metric is only compared between peers belonging to the same AS. rde
rib
name [no evaluate
]rde
rib
name [rtable
number]- Create an additional RIB named name. The degree to
which its routes may be utilized is configurable. They may be excluded
from the decision process that selects usable routes with the
no evaluate
flag, and this precludes their export to any kernel routing table. By default its routes will be evaluated, but not exported to the kernel. They may be both evaluated and exported if associated with a givenrtable
number, which must belong to the routing domain that bgpd(8) was started in. This table will not be consulted during nexthop verification unless it is the one that bgpd(8) was started in. It is unnecessary to createAdj-RIB-In
andLoc-RIB
, which are created automatically and used by default. rde
route-age
(ignore
|evaluate
)- If set to
evaluate
, the route decision process will also consider the age of the route in addition to its path attributes, giving preference to the older, typically more stable, route. This renders the decision process nondeterministic. The default isignore
. reject
as-set
(yes
|no
)- If set to
yes
, AS paths attributes containing AS_SET path segments will be rejected and all prefixes will be treated as withdraws. The default isno
. router-id
dotted-quad- Set the BGP router ID, which must be non-zero and should be unique within
the AS. By default, the router ID is the highest IPv4 address assigned to
the local machine.
router-id 10.0.0.1
rtable
number- Work with the given kernel routing table instead of the default table,
which is the one
bgpd(8) was started in. For nexthop verification,
bgpd(8) will always consult the default table. This is the same as
using the following syntax:
rde rib Loc-RIB rtable number
socket
"path" [restricted
]- Create a control socket at path. If
restricted
is specified, a restricted control socket will be created. By default /var/run/bgpd.sock.<rdomain> is used where <rdomain> is the routing domain in which bgpd(8) has been started. By default, no restricted socket is created. transparent-as
(yes
|no
)- If set to
yes
, AS paths to EBGP neighbors are not prepended with the local AS. The default isno
.
SET CONFIGURATION
bgpd(8) supports the efficient lookup of data within named
sets. An
as-set
, a prefix-set
, and an
origin-set
store AS numbers, prefixes, and
prefixes/source-as pairs, respectively. Such sets may be referenced by
filter rules; see the FILTER section for
details. It is more efficient to evaluate a set than a long series of rules
for filtering each of its members.
One single roa-set
may be defined, against
which bgpd(8) will validate the origin of each prefix. The
roa-set
and the aspa-set
are
merged with the corresponding tables received via
rtr
sessions.
A set definition can span multiple lines, and an optional comma is allowed between elements. The same set can be defined more than once, in this case the definitions are merged into one common set.
as-set
name{
as-number ...}
- An
as-set
stores AS numbers, and can be used with the AS specific parameter in FILTER rules. aspa-set
{
customer-as
as-number [expires
seconds]provider-as
{
as-number...
} ...
}
- The
aspa-set
holds a collection of Validated ASPA Payloads (VAPs). Each as AS_PATH received from an eBGP peer is checked against theaspa-set
, and the ASPA Validation State (AVS) is set.expires
can be set to the seconds since Epoch until when this VAP is valid.aspa-set { customer-as 64511 provider-as { 64496 65496 } customer-as 64496 provider-as { 65496 64544 } }
origin-set
name{
address/
lenmaxlen
mlensource-as
asn ...}
- An
origin-set
stores prefix/source-as pairs, and can be used to filter on the combination by using theorigin-set
parameter in FILTER rules.origin-set private { 10.0.0.0/8 maxlen 24 source-as 64511 203.0.113.0/24 source-as 64496 }
prefix-set
name{
address/
len ...}
- A
prefix-set
stores network prefixes and can be used in place of theprefix
parameter in FILTER rules, and innetwork
statements. A prefix can be followed by the prefixlen operators listed for theprefix
parameter in the PARAMETERS section.The first example below creates a set of prefixes called “private”, to hold a number of RFC 1918 private network blocks. The second example shows the use of prefixlen operators.
prefix-set private { 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, fc00::/7 } prefix-set as64496set { 192.0.2.0/24 prefixlen >= 26, 2001:db8::/32 or-longer }
roa-set
{
address/
len [maxlen
mlen]source-as
asn [expires
seconds] ...}
- The
roa-set
holds a collection of Validated ROA Payloads (VRPs). Each received prefix is checked against theroa-set
, and the Origin Validation State (OVS) is set.expires
can be set to the seconds since Epoch until when this VRP is valid.roa-set { 192.0.2.0/23 maxlen 24 source-as 64511 203.0.113.0/24 source-as 64496 }
rtr
address{
...}
- The
rtr
block specifies a RPKI to Router (RTR) session. RTR sessions provide another means to load VRP sets into bgpd(8). Changes propagated via the RTR protocol do not need a config reload and are immediately applied. The union of all VRP sets received viartr
sessions and the entries in theroa-set
is used to validate the origin of routes. The rtr session properties are as follows:descr
description- Add a description. The description is used in logging and status reports, but has no further meaning for bgpd(8).
local-address
address- Bind to the specific IP address before opening the TCP connection to the rtr server.
port
number- Specify the TCP destination port for the rtr
session. If not specified, the default
port
is 323.
NETWORK AND FLOWSPEC ANNOUNCEMENTS
network
statements specify the networks
that bgpd(8) will announce as its own. An announcement must also be
permitted by the FILTER rules. By default
bgpd(8) announces no networks.
network
address/
prefix [set ...
]- Announce the specified prefix as belonging to our AS.
network
(inet
|inet6
)connected
[set ...
]- Announce routes to directly attached networks.
network prefix-set
name [set ...
]- Announce all networks in the prefix-set name.
network
(inet
|inet6
)priority
number [set ...
]- Announce routes having the specified priority.
network
(inet
|inet6
)rtlabel
label [set ...
]- Announce routes having the specified label.
network
(inet
|inet6
)static
[set ...
]- Announce all static routes.
Each network
statement may set default
AS path attributes:
network 192.168.7.0/24 set localpref 220
See also the ATTRIBUTE SET section.
flowspec
statements specify the flowspec
rules that bgpd(8) will announce as its own. By default
bgpd(8) announces no flowspec rules.
flowspec
(inet
|inet6
) rule [set ...
]- Announce an IPv4 or IPv6 specific flowspec rule including the AS path attributes specified by set.
The following rule parameters can be set. Most number arguments in the below rules can be specified as a list of ranges enclosed in curly brackets using these operators:
= (equal, default) != (unequal) < (less than) <= (less than or equal) > (greater than) >= (greater than or equal) - (range including boundaries) >< (except range)
‘><’, and ‘-’ are binary operators (they take two arguments).
from
source [port
list]to
dest [port
list]- This rule applies only to packets with the specified source or destination
addresses and ports. Addresses can be specified in CIDR notation (matching
netblocks) or using
any
to match any address. In most cases ato
address must be specified and be part of the announced networks.Ports can be specified either by number or by name. For example, port 80 can be specified as
www
. For a list of all port name to number mappings see the file /etc/services. flags
a/b- This rule only applies to TCP packets that have the flags a set out of set b. Flags not specified in b are ignored. The flags are: (F)IN, (S)YN, (R)ST, (P)USH, (A)CK, (U)RG, (E)CE, and C(W)R.
fragment
a/b- This rule only applies to fragmented packets which match the specified flags. The flags are: (D)on't fragment, (I)s fragment, (F)irst fragment, and (L)ast fragment.
icmp-type
type [code
code]icmp6-type
type [code
code]- This rule only applies to ICMP or ICMP6 packets with the specified type and code. Text names for ICMP types and codes are listed in icmp(4) and icmp6(4).
length
pktlen- This rule applies only to packets matching the specified pktlen.
proto
protocol- This rule applies only to packets of this protocol. Common protocols are ICMP, ICMP6, TCP, and UDP. For a list of all the protocol name to number mappings see the file /etc/protocols.
tos
string|number- This rule applies to packets with the specified TOS bits set.
string may be one of
critical
,inetcontrol
,lowdelay
,netcontrol
,throughput
,reliability
, or one of the DiffServ Code Points:ef
,af11
...af43
,cs0
...cs7
; number may be either a hex or decimal number.
The action taken when a flowspec rules matches depends on extended
communities. For example to block all traffic either
ext-community
flow-rate
as-number:0 or ext-community
flow-pps
as-number:0 need to
be set.
MPLS VPN CONFIGURATION
A vpn
section configures a router to
participate in an MPLS Virtual Private Network. It specifies an
mpe(4) interface to use, a description, and various properties of the
VPN:
vpn "description" on mpe1 { rd 65002:1 import-target rt 65002:42 export-target rt 65002:42 network 192.168.1/24 }
bgpd(8) will not exchange VPN routes with a neighbor by default, see the NEIGHBORS AND GROUPS section. The description is used when logging but has no further meaning to bgpd(8).
The mpe(4) interface will be used as the outgoing interface for routes to the VPN, and local networks will be announced with the MPLS label specified on the interface. The interface can provide VPN connectivity for another rdomain by being configured in that rdomain. The required rdomain must be configured on the interface before bgpd(8) uses it. Multiple VPNs may be connected to a single rdomain, including the rdomain that bgpd(8) is running in.
An example hostname.if(5) configuration for an mpe(4) interface providing connectivity to rdomain 1:
rdomain 1 mplslabel 2000 inet 192.198.0.1 255.255.255.255 up
The VPN properties are as follows:
export-target
subtype as-number:localexport-target
subtype IP:local- Classify announced networks by tagging them with an extended
community of the given arguments. The community
subtype should be a route target,
rt
, to ensure interoperability. The arguments are further detailed in the ATTRIBUTE SET section. More than oneexport-target
can be specified. fib-update
(yes
|no
)- If set to
no
, do not update the Forwarding Information Base, a.k.a. the kernel routing table. The default isyes
. import-target
subtype as-number:localimport-target
subtype IP:local- The rdomain imports only those prefixes tagged with an
extended community matching an
import-target
. The community subtype should be a route target,rt
, to ensure interoperability. The arguments are further detailed in the ATTRIBUTE SET section. More than oneimport-target
can be specified. network
argument ...- Announce the given networks within this VPN; see the NETWORK ANNOUNCEMENTS section.
rd
as-number:localrd
IP:local- The Route Distinguisher
rd
supplies BGP with namespaces to disambiguate VPN prefixes, as these needn't be globally unique. Unlike route targets, therd
neither identifies the origin of the prefix nor controls into which VPNs the prefix is distributed. The as-number or IP of ard
should be set to a number or IP that was assigned by an appropriate authority, whereas local can be chosen by the local operator.
NEIGHBORS AND GROUPS
bgpd(8) establishes TCP connections to other BGP speakers called
neighbors. A neighbor and its properties are specified by
a
neighbor
section:
neighbor 10.0.0.2 { remote-as 65002 descr "a neighbor" }
Neighbors placed within a
group
section
inherit the properties common to that group:
group "peering AS65002" { remote-as 65002 neighbor 10.0.0.2 { descr "AS65002-p1" } neighbor 10.0.0.3 { descr "AS65002-p2" } }
An entire network of neighbors may be accommodated by specifying an address/netmask pair:
neighbor 10.0.0.0/8
This is a
template that
recognises as a neighbor any connection from within the given network. Such
neighbors inherit their template's properties, except for their IP address.
A template may omit remote-as
;
bgpd(8) then accepts any AS presented by the neighbor in the
OPEN message.
The neighbor properties are as follows:
announce
(IPv4
|IPv6
) (none
|unicast
|vpn
|flowspec
)- For the given address family, control which
subsequent
address families are announced during the capabilities
negotiation. Only routes for that address family and subsequent address
families will be announced and processed.
At the moment, only
none
, which disables the announcement of that address family,unicast
,vpn
, which allows the distribution of BGP MPLS VPNs, andflowspec
, which allows the distribution of Flow Specification Rules, are supported.The default is
unicast
for the same address family of the session. announce add-path recv
(yes
|no
)- If set to
yes
, the receive add-path capability is announced, which allows reception of multiple paths per prefix. The default isno
. announce add-path send
(no
|all
)announce add-path send
(best
|ecmp
|as-wide-best
) [plus
num] [max
num]- If set to
all
,best
,ecmp
, oras-wide-best
, the send add-path capability is announced, which allows sending multiple paths per prefix. The paths sent depend on which mode is selected:no
- do not advertise add-path send capability
all
- send all valid paths
best
- send the best path
ecmp
- send paths with equal nexthop cost
as-wide-best
- send paths where the first 8 checks of the decision process match
plus
allows the inclusion of additional backup paths and works forbest
,ecmp
, andas-wide-best
.max
can be used to limit the total amount of paths sent forecmp
andas-wide-best
. Right nowecmp
andas-wide-best
are equivalent. The default isno
. Ifadd-path
send
is active then the setting ofrde
evaluate
is ignored. announce as-4byte
(yes
|no
)- If set to
no
, the 4-byte AS capability is not announced and so native 4-byte AS support is disabled. The default isyes
. announce capabilities
(yes
|no
)- If set to
no
, capability negotiation is disabled during the establishment of the session. This can be helpful to connect to old or broken BGP implementations. The default isyes
. announce enhanced refresh
(yes
|no
)- If set to
yes
, the enhanced route refresh capability is announced. The default isno
. announce policy
(yes
|no
|enforce
)- If set to
yes
, add the open policy role capability. If the role of the neighbor does not correspond to the expected role then the session will be closed. Ifenforce
is set the session will only establish if the neighbor also announces the open policy capability. The default isno
. announce refresh
(yes
|no
)- If set to
no
, the route refresh capability is not announced. The default isyes
. announce restart
(yes
|no
)- If set to
no
, the graceful restart capability is not announced. Currently only the End-of-RIB marker is supported and announced by therestart
capability. The default isyes
. as-override
(yes
|no
)- If set to
yes
, all occurrences of the neighbor AS in the AS path will be replaced with the local AS before running the filters. The Adj-RIB-In still holds the unmodified AS path. The default value isno
. demote
group- Increase the carp(4) demotion counter on the given interface group,
usually carp, when the session is not in state
ESTABLISHED. The demotion counter will be increased as
soon as bgpd(8) starts and decreased 60 seconds after the session went to
state ESTABLISHED. For neighbors added at runtime, the
demotion counter is only increased after the session has been
ESTABLISHED at least once before dropping.
For more information on interface groups, see the
group
keyword in ifconfig(8). depend on
interface- The neighbor session will be kept in state IDLE as long
as interface reports no link. For
carp(4) interfaces, no link means that the interface is currently
backup.
This is primarily intended to be used with
carp(4) to reduce failover times.
The state of the network interfaces on the system can be viewed using the
show interfaces
command to bgpctl(8). descr
description- Add a description. The description is used when logging neighbor events, in status reports, for specifying neighbors, etc., but has no further meaning to bgpd(8).
down
[reason]- Do not start the session when
bgpd(8) comes up but stay in IDLE. If the session
is cleared at runtime, after a
down
reason was configured at runtime, the reason is sent as Administrative Shutdown Communication. The reason cannot exceed 255 octets. dump
(all
|updates
) (in
|out
) file [interval]- Dump ongoing BGP activity for a particular neighbor. See also the
dump
setting in GLOBAL CONFIGURATION. enforce local-as
(yes
|no
)- If set to
no
, AS paths will not be checked for AS loop detection. This feature is similar to allowas-in in some other BGP implementations. Since there is no AS path loop check, this feature is dangerous, and requires you to add filters to prevent receiving your own prefixes. The default value isyes
. enforce neighbor-as
(yes
|no
)- If set to
yes
, AS paths whose leftmost AS is not equal to the remote AS of the neighbor are rejected and a NOTIFICATION is sent back. The default value for IBGP peers isno
otherwise the default isyes
. export
(none
|default-route
)- If set to
none
, no UPDATE messages will be sent to the neighbor. If set todefault-route
, only the default route will be announced to the neighbor. holdtime
seconds- Set the holdtime in seconds. Inherited from the global configuration if not given.
holdtime min
seconds- Set the minimal acceptable holdtime. Inherited from the global configuration if not given.
ipsec
(ah
|esp
) (in
|out
)spi
spi-number authspec [encspec]- Enable IPsec with static keying. There must be at least two
ipsec
statements per peer with manual keying, one per direction. authspec specifies the authentication algorithm and key. It can besha1 <key> md5 <key>
encspec specifies the encryption algorithm and key.
ah
does not support encryption. Withesp
, encryption is optional. encspec can be3des <key> 3des-cbc <key> aes <key> aes-128-cbc <key>
Keys must be given in hexadecimal format. After changing settings, a session needs to be reset to use the new keys. The
ipsec
flows only work with session using the default port 179. ipsec
(ah
|esp
)ike
- Enable IPsec with dynamic keying. In this mode,
bgpd(8) sets up the flows, and a key management daemon such as
isakmpd(8) is responsible for managing the session keys. With
isakmpd(8), it is sufficient to copy the peer's public key, found
in /etc/isakmpd/local.pub, to the local machine.
It must be stored in a file named after the peer's IP address and must be
stored in /etc/isakmpd/pubkeys/ipv4/. The local
public key must be copied to the peer in the same way. As
bgpd(8) manages the flows on its own, it is sufficient to restrict
isakmpd(8) to only take care of keying by specifying the flags
-Ka
. This can be done in rc.conf.local(8). After starting the isakmpd(8) and bgpd(8) daemons on both sides, the session should be established. After changing settings, a session needs to be reset to use the new keys. Theipsec
flows only work with session using the default port 179. local-address
addressno local-address
- When bgpd(8) initiates the TCP connection to the neighbor system, it
normally does not bind to a specific IP address. If a
local-address
is given, bgpd(8) binds to this address first.no local-address
reverts back to the default. local-as
as-number [as-number]- Set the AS number sent to the remote system. Used as described above under
GLOBAL CONFIGURATION option
AS
.Since there is no AS path loop check, this option is dangerous, and requires you to add filters to prevent receiving your ASNs. Intended to be used temporarily, for migrations to another AS.
log no
- Disable neighbor specific logging.
log updates
- Log received and sent updates for this neighbor.
max-prefix
number [restart
number]- Terminate the session when the maximum number of
prefixes received is exceeded (no such limit is imposed by default). If
restart
is specified, the session will be restarted after number minutes. max-prefix
numberout
[restart
number]- Terminate the session when the maximum number of
prefixes sent is exceeded (no such limit is imposed by default). If
restart
is specified, the session will be restarted after number minutes. multihop
hops- Neighbors not in the same AS as the local
bgpd(8) normally have to be directly connected to the local
machine. If this is not the case, the
multihop
statement defines the maximum hops the neighbor may be away. passive
- Do not attempt to actively open a TCP connection to the neighbor system.
port
port- Connect to the peer using port instead of the default BGP port 179.
reject
as-set
(yes
|no
)- If set to
yes
, AS paths attributes containing AS_SET path segments will be rejected and all prefixes will be treated as withdraws. The default is inherited from the globalreject
as-set
setting. remote-as
as-number- Set the AS number of the remote system.
rde
evaluate
(default
|all
)- If set to all, keep evaluating alternative paths in
case the selected path is filtered out. By default if a path is filtered
by the output filters then no alternative path is sent to this peer. The
default is inherited from the global
rde
evaluate
setting. rib
name- Bind the neighbor to the specified RIB.
role
role- Set the local role for this eBGP session. Setting a role is required for
ASPA verification, the open policy role capability and Only-To-Customer
(OTC) attribute of RFC 9234. The role can be one of
none, provider,
customer, rs,
rs-client, or peer. If the
role is set to none the
announce
policy
will also be disabled. On iBGP session the role setting is ignored and forced to none. route-reflector
[address]- Act as an RFC 4456 route-reflector for this neighbor. An optional cluster ID can be specified; otherwise the BGP ID will be used.
set
attribute ...- Set the AS path attributes to some default per
neighbor
orgroup
block:set localpref 300
See also the ATTRIBUTE SET section. Set parameters are applied to the received prefixes; the only exceptions are
prepend-self
,nexthop no-modify
andnexthop self
. These sets are rewritten into filter rules and can be viewed with “bgpd -nv”. tcp md5sig password
secrettcp md5sig key
secret- Enable TCP MD5 signatures per RFC 2385. The shared secret can either be
given as a password or hexadecimal key.
tcp md5sig password mekmitasdigoat tcp md5sig key deadbeef
transparent-as
(yes
|no
)- If set to
yes
, AS paths to EBGP neighbors are not prepended with the local AS. The default is inherited from the globaltransparent-as
setting. ttl-security
(yes
|no
)- Enable or disable ttl-security. When enabled, outgoing packets are sent
using a TTL of 255 and a check is made against an incoming packet's TTL.
For directly connected peers, incoming packets are required to have a TTL
of 255, ensuring they have not been routed. For multihop peers, incoming
packets are required to have a TTL of 256 minus multihop distance,
ensuring they have not passed through more than the expected number of
hops. The default is
no
.
FILTER
bgpd(8) filters all BGP UPDATE messages, including its own announcements, and blocks them by default. Filter rules may match on neighbor, direction, prefix or AS path attributes. Filter rules may also modify AS path attributes.
For each UPDATE processed by the filter, the
filter rules are evaluated in sequential order, from first to last. The last
matching allow
or deny
rule
decides what action is taken. The default action is to deny.
The following actions can be used in the filter:
allow
- The UPDATE is passed.
deny
- The UPDATE is blocked.
match
- Apply the filter attribute set without influencing the filter decision.
PARAMETERS
The rule parameters specify the UPDATES to which a rule applies. An UPDATE always comes from, or goes to, one neighbor. Most parameters are optional, but each can appear at most once per rule. If a parameter is specified, the rule only applies to packets with matching attributes.
- as-type [operator] as-number
- as-type
as-set
name - This rule applies only to UPDATES where the
AS path matches. The part of the AS
path specified by the as-type is matched against
the as-number or the
as-set
name:AS
- (any part)
peer-as
- (leftmost AS number)
source-as
- (rightmost AS number)
transit-as
- (all but the rightmost AS number)
as-number is an AS number as explained above under GLOBAL CONFIGURATION. It may be set to
neighbor-as
, which is expanded to the current neighbor remote AS number, orlocal-as
, which is expanded to the locally assigned AS number.When specifying an
as-set
name, the AS path will instead be matched against all the AS numbers in the set.The operator can be unspecified (this case is identical to the equality operator), or one of the numerical operators
= (equal) != (unequal) - (range including boundaries) >< (except range)
>< and - are binary operators (they take two arguments); with these, as-number cannot be set to
neighbor-as
.Multiple as-number entries for a given type or as-type as-number entries may also be specified, separated by commas or whitespace, if enclosed in curly brackets:
deny from any AS { 1, 2, 3 } deny from any { AS 1, source-as 2, transit-as 3 } deny from any { AS { 1, 2, 3 }, source-as 4, transit-as 5 }
avs
(valid
|unknown
|invalid
)- This rule applies only to UPDATES where the ASPA Validation State (AVS) matches.
community
as-number:
localcommunity
name- This rule applies only to UPDATES where the
community
path attribute is present and matches. Communities are specified as as-number:local, where as-number is an AS number and local is a locally significant number between zero and65535
. Both as-number and local may be set to ‘*’ to do wildcard matching. Alternatively, well-known communities may be given by name instead and includeBLACKHOLE
,GRACEFUL_SHUTDOWN
,NO_EXPORT
,NO_ADVERTISE
,NO_EXPORT_SUBCONFED
, andNO_PEER
. Both as-number and local may be set toneighbor-as
, which is expanded to the current neighbor remote AS number, orlocal-as
, which is expanded to the locally assigned AS number. large-community
as-number:local:local- This rule applies only to UPDATES where the
Large community
path attribute is present and matches. Communities are specified as as-number:local:local, where as-number is an AS number and local is a locally significant number between zero and4294967295
. Both as-number and local may be set to ‘*’ to do wildcard matching,neighbor-as
, which is expanded to the current neighbor remote AS number, orlocal-as
, which is expanded to the locally assigned AS number. ext-community
subtype as-number:localext-community
subtype IP:localext-community
subtype numvalueext-community
ovs
(valid
|not-found
|invalid
)- This rule applies only to UPDATES where the
extended community path attribute is present and
matches. Extended Communities are specified by a
subtype and normally two values, a globally unique
part (e.g. the AS number) and a local part. Both
as-number and local may be set
to
neighbor-as
, which is expanded to the current neighbor remote AS number, orlocal-as
, which is expanded to the locally assigned AS number. Wildcard matching is supported for local, numvalue and subtype. If wildcard matching is used on the subtype then numvalue also needs to be set to ‘*’. See also the ATTRIBUTE SET section for further information about the encoding. - (
from
|to
) peer - This rule applies only to UPDATES coming from, or going
to, this particular neighbor. This parameter must be specified.
peer is one of the following:
any
- Any neighbor will be matched.
ibgp
- All IBGP neighbors will be matched.
ebgp
- All EBGP neighbors will be matched.
- address
- Neighbors with this address will be matched.
group
descr- Neighbors in this group will be matched.
AS
as-number- Neighbors with this AS will be matched.
Multiple peer entries may also be specified, separated by commas or whitespace, if enclosed in curly brackets:
deny from { 128.251.16.1, 251.128.16.2, group hojo }
- (
inet
|inet6
) - Match only routes in the IPv4 or IPv6 address families, respectively.
inet
is an alias for "prefix 0.0.0.0/0 prefixlen >= 0";inet6
is an alias for "prefix ::/0 prefixlen >= 0". max-as-len
len- This rule applies only to UPDATES where the AS path has more than len elements.
max-as-seq
len- This rule applies only to UPDATES where a single AS number is repeated more than len times.
max-communities
|max-large-communities
|max-ext-communities
num- This rule applies only to UPDATES where the Basic, Large, or Extended Community attribute has more than num elements.
nexthop
address- This rule applies only to UPDATES where the nexthop is equal to address. The address can be set to neighbor in which case the nexthop is compared against the address of the neighbor. Nexthop filtering is not supported on locally announced networks and one must take into consideration previous rules overwriting nexthops.
origin-set
name- This rule applies only to UPDATES that match the given origin-set name.
ovs
(valid
|not-found
|invalid
)- This rule applies only to UPDATES where the Origin Validation State (OVS) matches.
prefix
address/
lenprefix
address/
lenprefixlen
rangeprefix
address/
lenor-longer
prefix
address/
lenmaxlen
mlen- This rule applies only to UPDATES for the specified
prefix.
Multiple entries may be specified, separated by commas or whitespace, if enclosed in curly brackets:
deny from any prefix { 192.168.0.0/16, 10.0.0.0/8 or-longer }
Multiple lists can also be specified, which is useful for macro expansion:
good="{ 192.168.0.0/16, 172.16.0.0/12, 10.0.0.0/8 }" bad="{ 224.0.0.0/4 prefixlen >= 4, 240.0.0.0/4 prefixlen >= 4 }" ugly="{ 127.0.0.1/8, 169.254.0.0/16 }" deny from any prefix { $good $bad $ugly }
Prefix length ranges are specified by using these operators:
= (equal) != (unequal) < (less than) <= (less than or equal) > (greater than) >= (greater than or equal) - (range including boundaries) >< (except range)
>< and - are binary operators (they take two arguments). For instance, to match all prefix lengths >= 8 and <= 12, and hence the CIDR netmasks 8, 9, 10, 11 and 12:
prefixlen 8-12
Or, to match all prefix lengths < 8 or > 12, and hence the CIDR netmasks 0–7 and 13–32:
prefixlen 8><12
This will match all prefixes in the 10.0.0.0/8 netblock with netmasks longer than 16:
prefix 10.0.0.0/8 prefixlen > 16
or-longer
is a shorthand for:prefix
address/
lenprefixlen >=
lenmaxlen
mlen is a shorthand for:prefix
address/
lenprefixlen <=
mlen prefix-set
name [or-longer
]- This rule applies only to UPDATES that match the given
prefix-set name. With
or-longer
, the UPDATES will match any prefix in the prefix-set whereaddress
/
lenprefixlen >=
len quick
- If an UPDATE matches a rule which has the
quick
option set, this rule is considered the last matching rule, and evaluation of subsequent rules is skipped. rib
name- Apply rule only to the specified RIB. This only applies for received updates, so not for rules using the to peer parameter.
set
attribute ...- All matching rules can set the AS path attributes to some default. The set of every matching rule is applied, not only the last matching one. See also the following section.
ATTRIBUTE SET
AS path attributes can be modified with
set
.
set
can be used on
network
statements, in
neighbor
or group
blocks,
and on filter rules. Attribute sets can be expressed as lists.
The following attributes can be modified:
community
[delete] as-number:localcommunity
[delete] name- Set or delete the
COMMUNITIES
AS path attribute. Communities are specified as
as-number:local, where
as-number is an AS number and
local is a locally significant number between zero
and
65535
. Alternately, well-known communities may be specified by name:GRACEFUL_SHUTDOWN
,NO_EXPORT
,NO_ADVERTISE
,NO_EXPORT_SUBCONFED
, orNO_PEER
. Fordelete
, both as-number and local may be set to ‘*’ to do wildcard matching. large-community
[delete] as-number:local:locallarge-community
[delete] name- Set or delete the Large Communities path attribute.
Communities are specified as
as-number:local:local,
where as-number is an AS number and
local is a locally significant number between zero
and
4294967295
. Fordelete
, both as-number and local may be set to ‘*’ to do wildcard matching. ext-community
[delete] subtype as-number:localext-community
[delete] subtype IP:localext-community
[delete] subtype numvalueext-community
[delete]ovs
(valid
|not-found
|invalid
)- Set or delete the Extended Community AS path attribute.
Extended Communities are specified by a subtype and
normally two values, a globally unique part (e.g. the AS number) and a
local part. The type is selected depending on the encoding of the global
part. Two-octet AS Specific Extended Communities and Four-octet AS
Specific Extended Communities are encoded as
as-number:local. Four-octet
encoding is used if the as-number is bigger than
65535 or if the AS_DOT encoding is used. IPv4 Address Specific Extended
Communities are encoded as
IP:local. Opaque Extended
Communities are encoded with a single numeric value. The
ovs subtype can only be set to
valid, not-found, or
invalid. Currently the following subtypes are
supported:
bdc BGP Data Collection defgw Default Gateway esi-lab ESI Label esi-rt ES-Import Route Target l2vid L2VPN Identifier mac-mob MAC Mobility odi OSPF Domain Identifier ort OSPF Route Type ori OSPF Router ID ovs BGP Origin Validation State rt Route Target soo Route Origin / Source of Origin srcas Source AS vrfri VRF Route Import
Not all type and subtype value pairs are allowed by IANA and the parser will ensure that no invalid combination is created.
For
delete
, subtype, numvalue, or local, may be set to ‘*’ to do wildcard matching. If wildcard matching is used on the subtype then numvalue also needs to be set to ‘*’. localpref
number- Set the LOCAL_PREF AS path attribute. If number starts with a plus or minus sign, LOCAL_PREF will be adjusted by adding or subtracting number; otherwise it will be set to number. The default is 100.
med
numbermetric
number- Set the MULTI_EXIT_DISC AS path attribute. If number starts with a plus or minus sign, MULTI_EXIT_DISC will be adjusted by adding or subtracting number; otherwise it will be set to number.
origin
(igp
|egp
|incomplete
)- Set the ORIGIN AS path attribute to mark the source of this route as being injected from an igp protocol, an egp protocol or being an aggregated route.
nexthop
(address|blackhole
|reject
|self
|no-modify
)- Set the
NEXTHOP
AS path attribute to a different nexthop address or use blackhole or
reject routes.
blackhole
and reject only affect the FIB and will not alter the
nexthop address.
self
forces the nexthop to be set to the local interface address. If set to
no-modify, the nexthop attribute is not modified for
EBGP multihop sessions. By default EBGP multihop sessions use the local
interface address. On other IBGP and directly connected EBGP sessions
no-modify is ignored. The set
address is used on IBGP session and on directly
connected EBGP session if the address is part of the
connected network. On EBGP multihop session no-modify
has to be set to force the nexthop to address.
set nexthop 192.168.0.1 set nexthop blackhole set nexthop reject set nexthop no-modify set nexthop self
pftable
table- Add the prefix in the update to the specified pf(4) table, regardless of whether or not the path was selected for routing. This option may be useful in building realtime blacklists.
prepend-neighbor
number- Prepend the neighbor's AS number times to the AS path.
prepend-self
number- Prepend the local AS number times to the AS path.
rtlabel
label- Add the prefix to the kernel routing table with the specified label.
weight
number- The weight is used to tip prefixes with equally long AS paths in one or the other direction. A prefix is weighed at a very late stage in the decision process. If number starts with a plus or minus sign, the weight will be adjusted by adding or subtracting number; otherwise it will be set to number. Weight is a local non-transitive attribute, and is a bgpd(8)-specific extension. For prefixes with equally long paths, the prefix with the larger weight is selected.
FILES
- /etc/bgpd.conf
- bgpd(8) configuration file.
- /etc/examples/bgpd.conf
- Example configuration file.
SEE ALSO
strftime(3), ipsec(4), pf(4), rdomain(4), tcp(4), bgpctl(8), bgpd(8), ipsecctl(8), isakmpd(8), rc.conf.local(8)
HISTORY
The bgpd.conf
file format first appeared
in OpenBSD 3.5.