07-16-2007 07:19 AM - edited 03-03-2019 05:53 PM
Hi,
we would like to announce routes to provider A and B. detail please refer following.
for provider A
200.1.0.0/23
200.1.2.0/24
200.1.3.0/24
for provider B
200.1.0.0/24
200.1.1.0/24
200.1.2.0/24
200.1.3.0/24
We find that, we always anounce 4 routes to provider A. what wrong is it? please advice.
Best regards
----
router bgp 30x
!
neighbor 202.1.1.1 route-map Set_ASN_PA out
!
!
!
access-list 45 permit 200.1.0.0 0.0.1.255
!
access-list 55 permit 200.1.2.0 0.0.0.255
access-list 55 permit 200.1.3.0 0.0.0.255
!
ip as-path access-list 300 deny .*
ip as-path access-list 300 permit ^$
!
!
route-map Set_ASN_PA permit 10
match ip address 45
set as-path prepend 30x
!
route-map Set_ASN_PA permit 20
match ip address 55
!
route-map Set_ASN_PA permit 30
match as-path 300
!
07-16-2007 07:27 AM
ACL 45 allows 200.1.0.0/24 and 200.1.1.0/24 because of the wildcard mask 0.0.1.255. This is why provider A received the 4 routes.
Hope this helps,
07-16-2007 07:30 AM
hi,
how do we force it to /23? pls advise
best regards
07-16-2007 07:49 AM
Prior to announcing the /23 to your SP, you first need to inject the /23 into BGP a network statement and a static route to null0 as follow:
router bgp x
network 2000.1.0.0 mask 255.255.254.0
ip route 200.1.0.0 255.255.254.0 null0
Also, if you want to only allow the /23 (200.1.0.0/23) towards provider A and not the two /24s (200.1.0.0/24 and 200.1.1.0/24), you should use a prefix-list or an extended ACL instead of the standard ACL.
ip prefix-list test permit 200.1.0.0/23
Hope this helps,
07-16-2007 07:59 AM
Dear Hritter,
Thanks. We would like to use extended ACL to announce /23. Is it
access list 101 permit ip 200.1.0.0 0.0.1.255 255.255.254.0 0.0.0.0.
pls advise
07-16-2007 08:02 AM
Your ACL would work but I would rather configure it as follow:
access list 101 permit ip 200.1.0.0 0.0.0.0 255.255.254.0 0.0.0.0.
Hope this helps,
07-16-2007 08:39 AM
Hi,
We add the access but it displays as:
access-list 101 permit ip host 200.1.0.0 host 255.255.254.0
when I re-start the bgp, it does not announce 200.1.0.0/23 out but it announce 200.1.2.0/24, 200.1.3.0/24. It means that it announce two routes only. Any idea?
Best regards
07-16-2007 08:56 AM
It is normal behavior for the ACL to display as host as this means perfect match (or match all bits).
Can you post the new route-map and ACL and
the output of a "show ip bgp route-map Set_ASN_PA"
Regards,
07-16-2007 09:20 AM
Hi,
config is following:
---
access-list 145 permit ip 203.x.2.0 0.0.0.0 255.255.254.0 0.0.0.0
access-list 55 permit 203.x.0.0 0.0.0.255
access-list 55 permit 203.x.1.0 0.0.0.255
---
route-map Set_ASN_PA permit 10
match ip address 145
set as-path prepend 30x
!
route-map Set_ASN_PA permit 20
match ip address 55
!
route-map Set_ASN_PA permit 30
match as-path 200
---
BGP table version is 17687614, local router ID is 202.x.x.xx
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 203.x.0.0 203.x.y.94 0 32768 i
*> 203.x.1.0 0.0.0.0 0 32768 i
*> 203.x.2.0 203.x.y.95 0 32768 i
*> 203.x.3.0 0.0.0.0 0 32768 i
----
07-16-2007 09:29 AM
Did you generate the /23 using a network statement as I recommended previously? Can you post a "show ip bgp 203.x.2.0 255.255.254.0"
Also, note that the instance 30 in your routemap will allow everything that hasn't been allowed by the two previous instances.
Regards,
07-16-2007 09:38 AM
hi,
do we use
---
ip as-path access-list 300 deny .*
ip as-path access-list 300 permit ^$
route-map Set_ASN_PA permit 30
match as-path 300
---
07-16-2007 09:41 AM
Sorry. I meant to say everything that matches the as-path. Is 203.*.2.0/23 present in the BGP table?
Regards,
07-16-2007 09:49 AM
hi,
we check it, the result is
--
% Network not in table
---
it is because the network is inside our network
best regards
07-16-2007 09:52 AM
Did you use a network statement to generate 203.x.2.0/23 and also did you configure a matching route to null0?
Regards,
07-16-2007 09:56 AM
hi,
the network statement is /24, total 4 network statement there.
Do I change it to /23 and two /24?
If so, do it affect the provider B? please advise
Best regards
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