RSher@flagtelecom.com (Sher, Ryan) writes:
> Hi,
>
> I am trying to announce some aggregate routes from the core of my network
> (router: sfc1) to a router on the edge (router tok2). I dont understand the
> results I have seen. I have a simple policy on the RR in the core (sfc1)
> which takes the aggregate routes and advertises them to the clients on the
> edge (tok2). This policy works fine.
>
> The problem occurs on router tok2. It seems that out of two aggregates I
> advertise only one gets installed in the routing table while the other is
> hidden. I cant see any differences between these two aggregates, so it
> doesn't make sense to me why one would be installed in the Routing Table and
> the other not. The hidden route is telling me that the next hop is unusable,
> however tok2 does have a default route to this next hop (and the route that
> works has the identical next hop!)
>
> If I put a static route to the next hop both aggregates start working ...
> why?
>
The route resolver refuses to resolve 20.100.0.0/16 via 20.100.11.3,
through a route (in this case 0/0) that would be overshadowed by the
candidate being resolved.
Otherwise a route resolution loop would be created. In this case the
route would then resolve through itself.
Since you are running OSPF anyway it would probably be best to
advertise your BGP nexthops in OSPF instead of relying on a default
route.
regards,
Pedro.
> Thanks
> Ryan
>
> Here are some outputs comparing the two routes:
>
> lab@tok2# run show route 20.100.0.0/16 extensive hidden
>
> inet.0: 41 destinations, 60 routes (38 active, 0 holddown, 3 hidden)
> 20.100.0.0/16 (1 entry, 0 announced)
> BGP Preference: 170/-101
> Next hop type: Unusable
> State: <Hidden Int Ext>
> Local AS: 15412 Peer AS: 15412
> Age: 14:22
> Task: BGP_15412.20.100.11.3+179
> AS path: IAggregator: 15412 20.100.11.3
> Communities: 15412:700
> Localpref: 100
> Router ID: 20.100.11.3
> Indirect nexthops: 1
> Protocol Nexthop: 20.100.11.3 Indirect nexthop: 0 -
>
>
> [edit]
> lab@tok2# run show route 20.200.0.0/16 extensive
>
> inet.0: 39 destinations, 57 routes (36 active, 0 holddown, 3 hidden)
> 20.200.0.0/16 (1 entry, 1 announced)
> TSI:
> KRT in-kernel 20.200.0.0/16 -> {indirect(69)}
> Page 0 idx 1 Type 1 val 83c5e8c
> Nexthop: 20.100.11.3
> AS path: I
> Aggregator: 15412 20.100.11.3
> Communities: 15412:700
> Path 20.200.0.0 from 20.100.11.3 Vector len 4. Val: 1
> *BGP Preference: 170/-101
> Source: 20.100.11.3
> Nexthop: via t3-0/1/0.0, selected
> Protocol Nexthop: 20.100.11.3 Indirect nexthop: 8469110 69
> State: <Active Int Ext>
> Local AS: 15412 Peer AS: 15412
> Age: 22:02 Metric2: 12
> Task: BGP_15412.20.100.11.3+179
> Announcement bits (3): 0-KRT 4-BGP.0.0.0.0+179 5-Resolve
> inet.0
> AS path: IAggregator: 15412 20.100.11.3
> Communities: 15412:700
> Localpref: 100
> Router ID: 20.100.11.3
> Indirect nexthops: 1
> Protocol Nexthop: 20.100.11.3 Metric: 12 Indirect
> nexthop: 8469110 69
> Indirect path forwarding nexthops: 1
> Nexthop: via t3-0/1/0.0
>
>
> [edit]
> lab@tok2# run show route 20.100/16
>
> inet.0: 39 destinations, 57 routes (36 active, 0 holddown, 3 hidden)
> + = Active Route, - = Last Active, * = Both
>
> 20.100.16.1/32 *[Direct/0] 3d 04:13:05
> > via lo0.0
> 20.100.16.2/32 *[OSPF/10] 00:00:28, metric 2
> > via t3-0/1/1.0
> 20.100.50.0/30 *[Direct/0] 3d 03:17:43
> > via t3-0/1/0.0
> [OSPF/10] 00:00:33, metric 2
> > via t3-0/1/0.0
> 20.100.50.2/32 *[Local/0] 3d 04:13:05
> Local via t3-0/1/0.0
> 20.100.50.4/30 *[OSPF/10] 00:00:28, metric 4
> > via t3-0/1/1.0
> 20.100.50.8/30 *[Direct/0] 00:00:33
> > via t3-0/1/1.0
> [OSPF/10] 00:00:28, metric 2
> > via t3-0/1/1.0
> 20.100.50.9/32 *[Local/0] 00:00:33
> Local via t3-0/1/1.0
>
> [edit]
> lab@tok2# run show route 20.200/16
>
> inet.0: 39 destinations, 57 routes (36 active, 0 holddown, 3 hidden)
> + = Active Route, - = Last Active, * = Both
>
> 20.200.0.0/16 *[BGP/170] 00:20:11, localpref 100, from 20.100.11.3
> AS path: I
> > via t3-0/1/0.0
> 20.200.1.0/24 *[Direct/0] 3d 04:13:09
> > via fe-0/0/0.100
> 20.200.1.1/32 *[Local/0] 3d 04:13:09
> Local via fe-0/0/0.100
> 20.200.2.0/24 *[Direct/0] 3d 04:13:09
> > via fe-0/0/0.200
> 20.200.2.1/32 *[Local/0] 3d 04:13:09
> Local via fe-0/0/0.200
>
> [edit]
> lab@tok2# run show route 20.100.11.3
>
> inet.0: 41 destinations, 60 routes (38 active, 0 holddown, 3 hidden)
> + = Active Route, - = Last Active, * = Both
>
> 0.0.0.0/0 *[OSPF/10] 00:01:25, metric 12
> > via t3-0/1/0.0
>
>
> [edit]
> lab@tok2# run ping 20.100.11.3
> PING 20.100.11.3 (20.100.11.3): 56 data bytes
> 64 bytes from 20.100.11.3: icmp_seq=0 ttl=255 time=0.924 ms
> 64 bytes from 20.100.11.3: icmp_seq=1 ttl=255 time=0.848 ms
> 64 bytes from 20.100.11.3: icmp_seq=2 ttl=255 time=0.825 ms
>
>
>
>
>
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This archive was generated by hypermail 2b29 : Mon Aug 05 2002 - 10:42:36 EDT