On Fri, Nov 7, 2008 at 06:36, Nalkhande Tarique Abbas <[EMAIL PROTECTED]> wrote: > > Try Removing as-overide from R2.
Not if you want to advertise routes both from P2 to P3 and from P3 to P2. > > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Tomasz Opala > Sent: Friday, November 07, 2008 3:30 PM > To: juniper-nsp@puck.nether.net > Subject: [j-nsp] hidden route > > Hi gurus, > > Imagine following topology: > > P2(AS11)------R2(AS100)-------R3(AS100)-------P3(AS11) > > In order to advertise route 199.199.0.0/16 (static, redistriuted to BGP) > from router P2 to P3 (and some routes form P3 to P2), as-override has > been > configured on both R2 and R3: > > [EMAIL PROTECTED] show group p2 > type external; > peer-as 11; > as-override; > neighbor 192.168.1.2; > > [edit protocols bgp] > [EMAIL PROTECTED] > > [EMAIL PROTECTED] show group p3 > type external; > peer-as 11; > as-override; > neighbor 192.168.2.2; > > {master}[edit protocols bgp] > [EMAIL PROTECTED] > > > Route 199.199.0.0/16 is present in P3 routing table: > > [EMAIL PROTECTED]> show route protocol bgp terse 199.199/16 > > inet.0: 5 destinations, 5 routes (5 active, 0 holddown, 0 hidden) > + = Active Route, - = Last Active, * = Both > > A Destination P Prf Metric 1 Metric 2 Next hop AS > path > * 199.199.0.0/16 B 170 100 >192.168.2.1 100 > 100 I > > > Apparently the same route is advertised back, from R2 to P2 (it can be > seen > as a hidden route): > > [EMAIL PROTECTED]> show route hidden extensive > > inet.0: 8 destinations, 10 routes (8 active, 0 holddown, 1 hidden) > 199.199.0.0/16 (2 entries, 1 announced) > TSI: > KRT in-kernel 199.199.0.0/16 -> {} > Page 0 idx 0 Type 1 val 89768b8 > Nexthop: Self > AS path: [11] I > Communities: > Path 199.199.0.0 Vector len 4. Val: 0 > BGP > Next hop type: Router > Next-hop reference count: 1 > Source: 192.168.1.1 > Next hop: 192.168.1.2 via ge-1/2/1.2, selected > State: <Hidden Ext> > Inactive reason: Unusable path > Local AS: 11 Peer AS: 100 > Age: 13:52:22 > Task: BGP_100.192.168.1.1+60006 > AS path: 100 100 I > Router ID: 10.0.1.2 > > [EMAIL PROTECTED]> > > > Do you have any explanation of hidden route in P2? When using as-override like this, you will see hidden routes. What happens is that R2 receives and installs 199.199.0.0/16, then ebgp defaults to sending all installed routes to all ebgp peers and because as-override is configured, it strips AS11 from 199.199.0.0/16 before advertising it to P2. In the case of routes that R2 learned from P3 (via R3), this is good but for 199.199.0.0/16 it is not as good. P2 sees the route learned from R2 with a bgp/protocol next-hop of 192.168.1.2 (it's own address) and a physical/forwarding next-hop of interface ge-1/2/1.2 -- P2 knows that it can't reach itself out of that interface, so the route is hidden (Unusable path). This does not hurt anything though because R2 also has a good copy of that route [199.199.0.0/16 (2 entries, 1 announced)]. > > > Thanks, > Tomasz > _______________________________________________ > juniper-nsp mailing list juniper-nsp@puck.nether.net > https://puck.nether.net/mailman/listinfo/juniper-nsp > _______________________________________________ > juniper-nsp mailing list juniper-nsp@puck.nether.net > https://puck.nether.net/mailman/listinfo/juniper-nsp -- Chris Grundemann www.chrisgrundemann.com _______________________________________________ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp
