Hi all, I am having a problem with a J series router. I have a network as below:
R1---mp-ibgp----R2----multihop-ebgp----R3 The ebgp session between R2 and R3 is a normal EBGP multihop session. Let us say that it is between a PE and another box located somewhere on the internet. The mp-ibgp session between R1 and R2 is used for advertising vpnv4 prefixes. The BGP session between R2 and R3 terminates inside a VRF on R2. My problem is that R2 is rewriting the next-hop for the routes from R3 when it advertises them on to R1. I am definitely not setting next-hop self anywhere on R2. When I show received routes for the routes from R3, I get the following output: [EMAIL PROTECTED]> show route receive-protocol bgp z.z.z.z <snip> vrf-internet.inet.0: 216203 destinations, 363085 routes (216203 active, 0 holddown, 2 hidden) Prefix Nexthop MED Lclpref AS path * x.x.x.x/19 z.z.z.z 0 12345 I At this stage, the next-hop, z.z.z.z is intact and is the desired next-hop that I want advertised on to R1. When I show route extensive, things also *seem* (to me) to be ok (apologies if the following output is not very clean, I have also sanitised it a bit to replace IP addresses): [EMAIL PROTECTED]> show route table vrf-internet x.x.x.x/19 extensive ------------------------------------------------------------------------ vrf-internet.inet.0: 216037 destinations, 362760 routes (216037 active, 0 holddown, 2 hidden) x.x.x.x/19 (1 entry, 1 announced) TSI: Page 0 idx 0 Type 1 val c4b5f30 *BGP Preference: 170/-101 Next-hop reference count: 4 Source: z.z.z.z Next hop: 172.17.100.26 via fe-0/0/0.0, selected Label operation: Push 493, Push 109(top) Protocol next hop: z.z.z.z Indirect next hop: 8884af8 264765 State: <Active Ext> Peer AS: 12345 Age: 23:48:05 Metric: 0 Metric2: 1 Task: BGP_39532.z.z.z.z+37854 Announcement bits (3): 0-BGP RT Background 1-KRT 2-Resolve tree 2 AS path: 12345I Communities: 1234:1234 Localpref: 100 Router ID: 5.6.7.8 Indirect next hops: 1 Protocol next hop: z.z.z.z Metric: 1 Indirect next hop: 8884af8 264765 Indirect path forwarding next hops: 1 Next hop: 172.17.100.26 via fe-0/0/0.0 10.0.0.0/30 Originating RIB: vrf-internet.inet.0 Metric: 1 Node path count: 1 Indirect nexthops: 1 Protocol Nexthop: 3.3.3.3 Metric: 1 Push 493 Indirect nexthop: 89fae04 264578 Indirect path forwarding nexthops: 1 Nexthop: 172.17.100.26 via fe-0/0/0.0 3.3.3.3/32 Originating RIB: inet.3 Metric: 1 Node path count: 1 Forwarding nexthops: 1 Nexthop: 172.17.100.26 via fe-0/0/0.0 ----------------------------------------------------------------------- The protocol next-hop looks correct, z.z.z.z. However, when I show advertised routes towards R1, I see that the next-hop has been changed: [EMAIL PROTECTED]> show route advertising-protocol bgp 4.4.4.4 x.x.x.x/19 extensive vrf-internet.inet.0: 216241 destinations, 363161 routes (216241 active, 0 holddown, 2 hidden) * x.x.x.x/19 (1 entry, 1 announced) BGP group route-reflectors type Internal Route Distinguisher: 1111:1111 VPN Label: 107440 Nexthop: Self Flags: Nexthop Change MED: 0 Localpref: 100 AS path: [4321] 12345 I Communities: 1234:1234 target:1111:1111 Notice the lines that read "Nexthop: Self" and "Flags: Nexthop Change". The flag seems strange to me, does anybody know what it means? Nowhere in my policies do I set next-hop self: [EMAIL PROTECTED]> show configuration | match next-hop [EMAIL PROTECTED]> I have tried configuring, under the multihop bgp section, the parameter 'no-nexthop-change' but this does not have any effect ( I have set this both for the ibgp group and the ebgp group to no avail ). This behaviour seems unexpected to me - as though the box is automatically setting next-hop self for some reason. Normally in all of my experience (albeit with plain ibgp/ebgp setups) you need to explicitly turn on next-hop self. Does anybody have any idea why this is happening? My suspicion is it is definitely something to do with multihop bgp. Any help much appreciated, since at present I am completely stuck. And I am aware that under normal circumstances this would be desirable behaviour, but in this particular instance I have a specific requirement that the next-hop not be changed. Best regards, Anton _______________________________________________ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp