BGP Advertised Routes two Peering

[vasquezwilmer]

Dear all
I have issue with BGP behaviour. I have two BGP peering; from both I receive default route, but one of them,
AS 65472 is primary so I setup local preference in 200; it is because I want to use AS 65472 as internet
provider. The another one, AS 65472 is used as secundary internet access, but for internal network (private) is
used as primary. The issue is when try ping from LAN, can not reach internal network, seems to be that
becuase Local preference is setup within AS65472 and the packet try to go thru AS 65472 because local prefeence 200,
but I need that internal network go thru AS 65471.

I am sure that I am advertising network as I expect, but when is running BGP for both peering, it fails.

Here are go output for this situation:

7204VXR-SCT#sh ip bgp neighbors 172.16.40.37 received-routes
   Network          Next Hop            Metric LocPrf Weight Path
* i0.0.0.0          172.16.40.37             0    100      0 i

Total number of prefixes 1
7204VXR-SCT#sh ip bgp neighbors 172.16.40.37 advertised-routes
   Network          Next Hop            Metric LocPrf Weight Path
*> 10.10.200.0/30   0.0.0.0                  0         32768 i
*> 10.30.24.0/21    172.16.40.4              0         32768 i
*> 172.16.17.0/24   172.16.40.5              0         32768 i
*> 172.16.211.0/24  0.0.0.0                  0         32768 i
*> 172.18.56.16/29  0.0.0.0                  0         32768 i
*> 172.30.100.18/32 0.0.0.0                  0         32768 i
*> 172.31.0.20/30   0.0.0.0                  0         32768 i

7204VXR-SCT#sh ip bgp neighbors 190.97.254.241 received-routes
   Network          Next Hop            Metric LocPrf Weight Path
*  0.0.0.0          190.97.254.241                         0 65472 i

Total number of prefixes 1

   Network          Next Hop            Metric LocPrf Weight Path
*> 190.153.116.0/22 172.16.40.4              0         32768 i
*> 190.153.120.0/22 172.16.40.4              0         32768 i
*> 190.153.124.0/24 172.16.40.37            10         32768 i

router bgp 65471
 bgp log-neighbor-changes
 neighbor externalBGP peer-group
 neighbor externalBGP remote-as 65472
 neighbor externalBGP version 4
 neighbor internalBGP-SCT peer-group
 neighbor internalBGP-SCT remote-as 65471
 neighbor internalBGP-SCT version 4
 neighbor 172.16.40.37 peer-group internalBGP-SCT
 neighbor 190.97.254.241 peer-group viginet
 !
 address-family ipv4
 neighbor externalBGPsoft-reconfiguration inbound
 neighbor externalBGProute-map viginet-in in
 neighbor externalBGProute-map viginet-out out
 neighbor internalBGP-SCT soft-reconfiguration inbound
 neighbor internalBGP-SCT route-map internalBGP-SCT-out out
 neighbor 172.16.40.37 activate
 neighbor 190.97.254.241 activate
 no auto-summary
 no synchronization
 network 10.10.200.0 mask 255.255.255.252
 network 10.30.24.0 mask 255.255.248.0
 network 172.16.17.0 mask 255.255.255.0
 network 172.16.40.0 mask 255.255.255.0
 network 172.16.211.0 mask 255.255.255.0
 network 172.18.56.16 mask 255.255.255.248
 network 172.30.100.18 mask 255.255.255.255
 network 172.31.0.20 mask 255.255.255.252
 network 190.153.116.0 mask 255.255.252.0
 network 190.153.120.0 mask 255.255.252.0
 network 190.153.124.0 mask 255.255.255.0
 exit-address-family
!
ip route 172.16.40.36 255.255.255.252 Null0 250
ip route 190.153.116.0 255.255.252.0 172.16.40.4
ip route 190.153.120.0 255.255.252.0 172.16.40.4
!
ip prefix-list invalidas seq 10 permit 172.16.40.0/24
ip prefix-list invalidas seq 15 permit 10.30.24.0/21
ip prefix-list invalidas seq 20 permit 172.16.211.0/24
ip prefix-list invalidas seq 25 permit 172.18.56.16/29
ip prefix-list invalidas seq 30 permit 172.30.100.18/32
ip prefix-list invalidas seq 35 permit 10.10.200.0/30
ip prefix-list invalidas seq 40 permit 172.16.17.0/24
ip prefix-list invalidas seq 45 permit 172.31.0.20/30
!
ip access-list standard viginet-100
 permit 190.153.116.0 0.0.3.255
 permit 190.153.120.0 0.0.3.255
 permit 190.153.124.0 0.0.0.255
!
route-map externalBGP-out permit 10
 match ip address viginet-100
!
route-map externalBGP-in permit 10
 set local-preference 200
!

route-map internalBGP-SCT-out permit 10
 match ip address prefix-list invalidas
!

[Vasilii Mikhailovskii]

Hello.

If you want your internal network to go through peer 65471 (to 0.0.0.0/0), then why do you need AS 65472?

Could you please provide "show ip bgp 0.0.0.0/0"?

[ahmed]

Hi vasili,

i have looks like same problem, when i do show ip bgp 0.0.0.0/0, it says not advertise to any peer

[Vasilii Mikhailovskii]

Could you please provide "show ip bgp 0.0.0.0/0" + "show ip bgp summ" along with router bgp configuration?

Please clarify to which neighbour do you want to advertise the prefix.

[paul driver]

Hello
Just to confirm -
You have 2 local rtrs each with an ISP connection and both receiving default routes which are originating from ebgp peerings, and you have an ibgp connection between each local rtr?

I am assuming both of these local rtrs have internal connectivity to your LAN core via some IGP and possibly they are both advertising a default route into that igp with one of the two local rtrs showing up as the preferred path, maybe this one -7204VXR-SCT

Possible solution
Policy route on specific lan subnets and push that traffic out over the IGBP and onwards to the less preferred isp.

On your primary local router = 7204VXR-SCT

ip access-list standard STAN
permit x.x.x.x y.y.y.yy
route-map PBR
match ip address STAN
set ip next-hop 172.16.40.37 <IGBP peer>

interface x/x
description Link to LAN
ip policy route-map PBR


res
Paul