Hi All,
For a requirement I had, I wanted to test various regex combinations of AS-PATH Prepend matches using IOSXR RPL.
In case, someone else also has a similar situation, I thought of sharing the results.
Iosxr regex syntax: ([0-9]+)(_\1)(_\1)(_\1)$
- Matches a single AS
- Matches repeat (prepend)
- You can test with ^, $, [0-9]+, [0-9]* and (64514).
!---Test_AS-PATH-PREPENDed-Advertisement---!
RP/0/RP0/CPU0:rr-1#sh bgp ipv4 u neighbors 172.16.10.10 received routes
.......
Status codes: s suppressed, d damped, h history, * valid, > best
i - internal, r RIB-failure, S stale, N Nexthop-discard
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* 1.1.1.1/32 172.16.10.10 0 0 64514 64514 64514 64514 i
* 2.2.2.2/32 172.16.10.10 0 0 64514 64514 64514 64514 64514 i
* 3.3.3.3/32 172.16.10.10 0 0 64514 64514 64514 64514 64514 64514 i
Processed 3 prefixes, 3 paths
!--------------------------------------------------------------------------------------------------------!
REGEX Pattern: '^([0-9]+).........$'
!--------------------------------------------------------------------------------------------------------!
1)
conf t
route-policy AS-PREPEND
if as-path in (ios-regex '^([0-9]+)(_\1)(_\1)(_\1)(_\1)(_\1)$') then
set community (64514:64514)
endif
end-policy
commit
exit
Matches:
* 3.3.3.3/32 172.16.10.10 0 0 64514 64514 64514 64514 64514 64514 i
!--------------------------------------------------------------------------------------------------------!
2)
conf t
route-policy AS-PREPEND
if as-path in (ios-regex '^([0-9]+)(_\1)(_\1)(_\1)(_\1)$') then
set community (64514:64514)
endif
end-policy
commit
exit
Matches:
* 2.2.2.2/32 172.16.10.10 0 0 64514 64514 64514 64514 64514 i
!--------------------------------------------------------------------------------------------------------!
3)
conf t
route-policy AS-PREPEND
if as-path in (ios-regex '^([0-9]+)(_\1)(_\1)(_\1)$') then
set community (64514:64514)
endif
end-policy
commit
exit
Matches:
* 1.1.1.1/32 172.16.10.10 0 0 64514 64514 64514 64514 i
!--------------------------------------------------------------------------------------------------------!
REGEX Pattern: '^(64514).........$'
!--------------------------------------------------------------------------------------------------------!
1a)
conf t
route-policy AS-PREPEND
if as-path in (ios-regex '^(64514)(_\1)(_\1)(_\1)(_\1)(_\1)$') then
set community (64514:64514)
endif
end-policy
commit
exit
Matches:
* 3.3.3.3/32 172.16.10.10 0 0 64514 64514 64514 64514 64514 64514 i
!--------------------------------------------------------------------------------------------------------!
2a)
conf t
route-policy AS-PREPEND
if as-path in (ios-regex '^(64514)(_\1)(_\1)(_\1)(_\1)$') then
set community (64514:64514)
endif
end-policy
commit
exit
Matches:
* 2.2.2.2/32 172.16.10.10 0 0 64514 64514 64514 64514 64514 i
!--------------------------------------------------------------------------------------------------------!
3a)
conf t
route-policy AS-PREPEND
if as-path in (ios-regex '^(64514)(_\1)(_\1)(_\1)$') then
set community (64514:64514)
endif
end-policy
commit
exit
Matches:
* 1.1.1.1/32 172.16.10.10 0 0 64514 64514 64514 64514 i
!--------------------------------------------------------------------------------------------------------!
REGEX Pattern: '([0-9]+).........$'
!--------------------------------------------------------------------------------------------------------!
1b)
conf t
route-policy AS-PREPEND
if as-path in (ios-regex '([0-9]+)(_\1)(_\1)(_\1)(_\1)(_\1)$') then
set community (64514:64514)
endif
end-policy
commit
exit
Matches:
* 3.3.3.3/32 172.16.10.10 0 0 64514 64514 64514 64514 64514 64514 i
!--------------------------------------------------------------------------------------------------------!
2b)
conf t
route-policy AS-PREPEND
if as-path in (ios-regex '([0-9]+)(_\1)(_\1)(_\1)(_\1)$') then
set community (64514:64514)
endif
end-policy
commit
exit
Matches:
* 2.2.2.2/32 172.16.10.10 0 0 64514 64514 64514 64514 64514 i
* 3.3.3.3/32 172.16.10.10 0 0 64514 64514 64514 64514 64514 64514 i
!--------------------------------------------------------------------------------------------------------!
3b)
conf t
route-policy AS-PREPEND
if as-path in (ios-regex '([0-9]+)(_\1)(_\1)(_\1)$') then
set community (64514:64514)
endif
end-policy
commit
exit
Matches:
* 1.1.1.1/32 172.16.10.10 0 0 64514 64514 64514 64514 i
* 2.2.2.2/32 172.16.10.10 0 0 64514 64514 64514 64514 64514 i
* 3.3.3.3/32 172.16.10.10 0 0 64514 64514 64514 64514 64514 64514 i
!--------------------------------------------------------------------------------------------------------!
What I also wanted to test was {min,max} but could not get that working. I was trying it on 7.1.2 so not sure if this is not supported at all or may be in a different version. If any has any experience of using that, please do share.
Kind regards,
Abid Ghufran
