Not able to set outbound local preference

[Alberto Romano]

Hi all,

I need to add a new iBGP peer to our Route Reflector (RR), but not as reflector-client and modifing the outbound local preferenze with a route-map. I know that a RR can't modify the outbound local preference towards their clients, but in my scenario It should. But It isn't true. The new peer receive the route with a local preference value of 100 (default value). Why? What can I do? This is the configuration:

router bgp 9104
 bgp router-id 1.0.0.0
 bgp log-neighbor-changes
 neighbor RUPAR_MST peer-group
 neighbor RUPAR_MST remote-as 9104
 neighbor RUPAR_MST update-source Loopback0
 neighbor RUPAR_BCK peer-group
 neighbor RUPAR_BCK remote-as 9104
 neighbor RUPAR_BCK update-source Loopback0
 neighbor 195.60.156.3 peer-group RUPAR_MST
 neighbor 195.60.156.3 description EPO_MST
 neighbor 195.60.156.4 peer-group RUPAR_BCK
 neighbor 195.60.156.4 description EPO_BCK
 neighbor 195.60.156.5 peer-group RUPAR_MST
 neighbor 195.60.156.5 description QXN_MST
 neighbor 195.60.156.6 peer-group RUPAR_BCK
 neighbor 195.60.156.6 description QXN_BCK
 neighbor 195.60.156.7 remote-as 9104
 neighbor 195.60.156.7 update-source Loopback0
 !
 address-family ipv4
  neighbor RUPAR_MST route-reflector-client
  neighbor RUPAR_MST weight 200
  neighbor RUPAR_BCK route-reflector-client
  neighbor RUPAR_BCK weight 100
  neighbor 195.60.156.3 activate
  neighbor 195.60.156.4 activate
  neighbor 195.60.156.5 activate
  neighbor 195.60.156.6 activate
  neighbor 195.60.156.7 activate
  neighbor 195.60.156.7 route-map SET_LOCAL_PREF out
  no auto-summary
  no synchronization
 exit-address-family
!
ip prefix-list EPO_ORIGIN seq 5 permit 195.60.156.3/32
ip prefix-list EPO_ORIGIN seq 10 permit 195.60.156.4/32
!
ip prefix-list QXN_ORIGIN seq 5 permit 195.60.156.5/32
ip prefix-list QXN_ORIGIN seq 10 permit 195.60.156.6/32
!
route-map SET_LOCAL_PREF permit 10
 match ip route-source prefix-list EPO_ORIGIN
 set local-preference 105

route-map SET_LOCAL_PREF permit 20
 match ip route-source prefix-list QXN_ORIGIN
 set local-preference 150

Thanks in advance.

[Gaurav Mahajan]

share following outputs 

show ip route 195.60.156.3 

show ip route 195.60.156.4 

show ip bgp 195.60.156.3

show ip bgp 195.60.156.4

[Alberto Romano]

RR#show ip route 195.60.156.3
Routing entry for 195.60.156.3/32
  Known via "ospf 9104", distance 110, metric 2, type intra area
  Last update from 10.0.0.3 on FastEthernet0/0.307, 01:49:50 ago
  Routing Descriptor Blocks:
  * 10.0.0.3, from 3.0.0.0, 01:49:50 ago, via FastEthernet0/0.307
      Route metric is 2, traffic share count is 1

RR#show ip route 195.60.156.4
Routing entry for 195.60.156.4/32
  Known via "ospf 9104", distance 110, metric 2, type intra area
  Last update from 10.0.0.4 on FastEthernet0/0.307, 01:53:01 ago
  Routing Descriptor Blocks:
  * 10.0.0.4, from 4.0.0.0, 01:53:01 ago, via FastEthernet0/0.307
      Route metric is 2, traffic share count is 1

The last two commands are related to two not BGP routes, so:

RR#show ip bgp 195.60.156.3
% Network not in table

RR#show ip bgp 195.60.156.4
% Network not in table

[Gaurav Mahajan]

Hi Alberto Romano,

As route is not there in BGP table and can be seen only in the routing table known via OSPF 9104 it's not able to make any changes to the local preference.

what is the source of these routes, internal to your network or they are coming from outside.

do you need to redistribute these routes in bgp or advertise these routes using network statements in bgp.

Hope this helps !

Thanks,

Gaurav

[Alberto Romano]

It's clear, but you probably have misunderstood. The 195.60.156.3 and 195.60.156.4 are the loopbacks of our two reflector-clients that are advertising the BGP routes that I need to propagate to the new RR's peer (alias 195.60.156.7, but not reflector-client). The match statment in the route-map is based on two route-source prefix-lists so to limit the advertisements only to ones originated by 195.60.156.3 e 4 and not propagate all routes from other reflector-clients.

I hope I was clear.

[Alberto Romano]

From the RFC2796:

8. Implementation Considerations

   Care should be taken to make sure that none of the BGP path
   attributes defined above can be modified through configuration when
   exchanging internal routing information between RRs and Clients and
   Non-Clients. Their modification could potential result in routing
   loops.

   In addition, when a RR reflects a route, it should not modify the
   following path attributes: NEXT_HOP, AS_PATH, LOCAL_PREF, and MED.
   Their modification could potential result in routing loops.

About what the RFC said, It's impossible for a RR modify any BGP attributes for an advertised route to a client and non-client peer in the same AS. If I'm misunderstanding, please give me the correct point of view.

Thanks all guys!

[sarathpa]

Hi,

Could you please provide me the below output from the neighbor router (195.60.156.7)

1)show ip bgp 195.60.156.5

2)show ip bgp 195.60.156.6

Also need below output from this router

show ip bgp neighbors 192.168.156.7 advertised-routes

[Alberto Romano]

Hi... again, the 195.60.156.5 e 6 are not in the BGP table. These IPs are the loopback addresses of two peers that area advertising the routes I need to propagate to the new peer. To clarify the situation, this is the output of the "show ip bgp":

RR>sh ip bgp
BGP table version is 3, local router ID is 1.0.0.0
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
* i172.31.0.0       195.60.156.6             0    100    100 i
*>i                 195.60.156.5             0    100    200 i
* i192.168.1.0      195.60.156.4             0    100    100 i
*>i                 195.60.156.3             0    100    200 i

So the IPs you are interested in are the "next-hop" of the BGP routes advertised.

I can't provide the show output that you requested because, according to the RFC above, I've established an eBGP session between the RR and the new peer. So...

RR>sh ip bgp neighbors 10.10.10.7 advertised-routes
BGP table version is 3, local router ID is 1.0.0.0
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
*>i172.31.0.0       195.60.156.5             0    100    200 i
*>i192.168.1.0      195.60.156.3             0    100    200 i

Total number of prefixes 2

Thanks for your interest.