From: Volkov, Dmitry (IDS Canada) (dmitry_volkov@ca.ml.com)
Date: Sat Jul 05 2003 - 18:38:39 GMT-3
> -----Original Message-----
> From: Scott Morris [mailto:swm@emanon.com]
> Sent: Saturday, July 05, 2003 5:23 PM
> To: 'Brian McGahan'; 'Donny MATEO'; 'Volkov, Dmitry (IDS Canada)'
> Cc: ccielab@groupstudy.com; nobody@groupstudy.com
> Subject: RE: BGP peer establishment
>
>
> Right... Watch through a sniffer though. Which side initiates the
> connection?
>
> For more amusing results, try to change the non-default route to the
> other side and see what happens.
>
> I understood what you were saying just fine. :)
>
> Nope, not really... Check out your peer establishment with a
> sniffer...
> Check out which side is initiating the contact at that point.
> The side
> without the default route is the only one who will initiate.
>
> Interestingly enough, it is typically the side with the higher IP that
> initiates the connection, but after configuring BGP your
Both sides initiate TCP connections. Higher bgp router-id will win.
TCP session initiated from peer with lower bgp router-id will be closed.
If one side is blocked by firewall or has def route and doesn't have longer
match to the neighbor,
another side (assuming it has specific route to neighbor and is not blocked
by firewall) open BGP session.
> router will put
> the neighbor in an active state and after a while of not hearing from
> the other side (even if it has the lower ip) it gets kinda pissy and
> starts the connection itself. :)
>
> But either way the higher IP goes, the connection in your case will be
> initiated by the guy who has the non-default route attached. So if
> there was interpretation difficulty there, I apologize. But
> allow me to
> re-phrase... A peer will not be INITIATED using a default 0/0 route.
> It may be ACCEPTED because a tcp connection is a tcp connection
> regardless of how I get there.
>
> HTH,
>
> Scott
>
> -----Original Message-----
> From: Brian McGahan [mailto:brian@cyscoexpert.com]
> Sent: Saturday, July 05, 2003 4:55 PM
> To: swm@emanon.com; 'Donny MATEO'; 'Volkov, Dmitry (IDS Canada)'
> Cc: ccielab@groupstudy.com; nobody@groupstudy.com
> Subject: RE: BGP peer establishment
>
>
> Scott,
>
> I think you're misinterpreting what I'm saying. You can use a
> default route to establish BGP peering, as long as both sides are not
> using a default.
>
> HTH
>
> Brian McGahan, CCIE #8593
> Director of Design and Implementation
> brian@cyscoexpert.com
>
> CyscoExpert Corporation
> Internetwork Consulting & Training
> Toll Free: 866.CyscoXP
> Fax: 847.674.2625
>
>
> > -----Original Message-----
> > From: Scott Morris [mailto:swm@emanon.com]
> > Sent: Friday, July 04, 2003 3:03 PM
> > To: 'Brian McGahan'; 'Donny MATEO'; 'Volkov, Dmitry (IDS Canada)'
> > Cc: ccielab@groupstudy.com; nobody@groupstudy.com
> > Subject: RE: BGP peer establishment
> >
> > Correct. Any prefix longer than /0 would count as a "non-default"
> > route. :)
> >
> > Thanks for the output though!
> >
> > Scott
> >
> > -----Original Message-----
> > From: Brian McGahan [mailto:brian@cyscoexpert.com]
> > Sent: Friday, July 04, 2003 2:18 PM
> > To: 'Scott Morris'; 'Donny MATEO'; 'Volkov, Dmitry (IDS Canada)'
> > Cc: ccielab@groupstudy.com; nobody@groupstudy.com
> > Subject: RE: BGP peer establishment
> >
> >
> > Not necessarily. As long as one side of the connection has a
> longer
> > match than 0.0.0.0/0 adjacency can be established. Take
> the following
>
> > scenario:
> >
> > R1-16.0.0.0/8---R6---26.0.0.0/8---R2
> >
> > R1 is in AS 1, R2 is in AS 2. They are transitting R6 to peer.
> The
> > only route that R1 has to the 26.0.0.0/8 subnet is a default,
> while
> > R2 has a longer match to 16.0.0.0/8.
> >
> > R1#sh run | b router bgp
> > router bgp 1
> > bgp log-neighbor-changes
> > network 1.1.1.1 mask 255.255.255.255
> > neighbor 26.0.0.2 remote-as 2
> > neighbor 26.0.0.2 ebgp-multihop 255
> > !
> > ip route 0.0.0.0 0.0.0.0 16.0.0.6
> >
> > R2#sh run | b router bgp
> > router bgp 2
> > bgp log-neighbor-changes
> > network 2.2.2.2 mask 255.255.255.255
> > neighbor 16.0.0.1 remote-as 1
> > neighbor 16.0.0.1 ebgp-multihop 255
> > !
> > ip route 16.0.0.0 255.0.0.0 26.0.0.6
> >
> > R1#sh ip bgp sum | b Neighbor
> > Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down
> > State/PfxRcd
> > 26.0.0.2 4 2 11 11 3 0 0 00:06:32
> > 1
> >
> > R2#sh ip bgp sum | b Neighbor
> > Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down
> > State/PfxRcd
> > 16.0.0.1 4 1 12 12 3 0 0 00:07:10
> > 1
> >
> > R1#sh ip bgp
> > BGP table version is 3, local router ID is 16.0.0.1
> > Status codes: s suppressed, d damped, h history, * valid, >
> best, i -
> > internal Origin codes: i - IGP, e - EGP, ? - incomplete
> >
> > Network Next Hop Metric LocPrf Weight Path
> > *> 1.1.1.1/32 0.0.0.0 0 32768 i
> > *> 2.2.2.2/32 26.0.0.2 0 0 2 i
> >
> > R2#sh ip bgp
> > BGP table version is 3, local router ID is 26.0.0.2
> > Status codes: s suppressed, d damped, h history, * valid, >
> best, i -
> > internal Origin codes: i - IGP, e - EGP, ? - incomplete
> >
> > Network Next Hop Metric LocPrf Weight Path
> > *> 1.1.1.1/32 16.0.0.1 0 0 1 i
> > *> 2.2.2.2/32 0.0.0.0 0 32768 i
> >
> > R1#sh ip route
> > Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B -
> BGP
> > D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF
> inter area
> > N1 - OSPF NSSA external type 1, N2 - OSPF NSSA
> external type 2
> > E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
> > i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2,
> ia - IS-IS
> > inter area
> > * - candidate default, U - per-user static route, o - ODR
> > P - periodic downloaded static route
> >
> > Gateway of last resort is 16.0.0.6 to network 0.0.0.0
> >
> > C 16.0.0.0/8 is directly connected, FastEthernet0/6
> > 1.0.0.0/32 is subnetted, 1 subnets
> > C 1.1.1.1 is directly connected, Loopback0
> > 2.0.0.0/32 is subnetted, 1 subnets
> > B 2.2.2.2 [20/0] via 26.0.0.2, 00:06:08
> > S* 0.0.0.0/0 [1/0] via 16.0.0.6
> > R1#
> >
> > R2#sh ip route
> > Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B -
> BGP
> > D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF
> inter area
> > N1 - OSPF NSSA external type 1, N2 - OSPF NSSA
> external type 2
> > E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
> > i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2,
> ia - IS-IS
> > inter area
> > * - candidate default, U - per-user static route, o - ODR
> > P - periodic downloaded static route
> >
> > Gateway of last resort is not set
> >
> > S 16.0.0.0/8 [1/0] via 26.0.0.6
> > 1.0.0.0/32 is subnetted, 1 subnets
> > B 1.1.1.1 [20/0] via 16.0.0.1, 00:06:55
> > 2.0.0.0/32 is subnetted, 1 subnets
> > C 2.2.2.2 is directly connected, Loopback0
> > C 26.0.0.0/8 is directly connected, FastEthernet0/6
> >
> >
> > As you can see from the above output, as long as one side has a
> > longer match than 0, BGP adjacency can be established.
> >
> > HTH,
> >
> > Brian McGahan, CCIE #8593
> > Director of Design and Implementation
> > brian@cyscoexpert.com
> >
> > CyscoExpert Corporation
> > Internetwork Consulting & Training
> > Toll Free: 866.CyscoXP
> > Fax: 847.674.2625
> >
> >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf
> > Of
> > > Scott Morris
> > > Sent: Friday, July 04, 2003 8:57 AM
> > > To: 'Donny MATEO'; 'Volkov, Dmitry (IDS Canada)'
> > > Cc: ccielab@groupstudy.com; nobody@groupstudy.com
> > > Subject: RE: BGP peer establishment
> > >
> > > There must be a non-default route to reach the other side. So
> > anything
> > > other than a 0/0 route will work.
> > >
> > > Scott
> > >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf
> > Of
> > > Donny MATEO
> > > Sent: Friday, July 04, 2003 1:58 AM
> > > To: Volkov, Dmitry (IDS Canada)
> > > Cc: 'ccielab@groupstudy.com'; nobody@groupstudy.com
> > > Subject: Re: BGP peer establishment
> > >
> > >
> > > If I remember correctly there was an old thread
> discussing this. The
>
> > > conclusion is something like BGP need specific route to establish
> > > peering. Not sure if there is anymore information as to why and so
> on.
> > >
> > > Donny
> > >
> > >
> > >
> > >
> > >
> > > "Volkov, Dmitry
> > >
> > > (IDS Canada)" To:
> > > "'ccielab@groupstudy.com'" <ccielab@groupstudy.com>
> > >
> > > <dmitry_volkov@ca cc:
> > >
> > > .ml.com> Subject: BGP peer
> > > establishment
> > > Sent by:
> > >
> > > nobody@groupstudy
> > >
> > > .com
> > >
> > >
> > >
> > >
> > >
> > > 07/04/2003 06:22
> > >
> > > AM
> > >
> > > Please respond to
> > >
> > > "Volkov, Dmitry
> > >
> > > (IDS Canada)"
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > R5(172.50.50.5)---------(.1)pix(.10)--------(172.50.10.1)R1
> > >
> > > R5 can ping R1; R5 uses default route to reach R1. R5 can not
> > establish
> > > BGP peering with R1 until I put static route - more specific than
> > > 0.0.0.0 0.0.0.0 - WHY ?
> > >
> > > r5#sh ip bgp sum
> > > BGP router identifier 60.5.5.5, local AS number 55
> > > BGP table version is 1, main routing table version 1
> > >
> > > Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down
> > > State/PfxRcd
> > > 172.50.10.1 4 65 0 0 0 0 0 never
> > > Active
> > >
> > > r5#sh ip ro
> > > <snip>
> > > R* 0.0.0.0/0 [120/1] via 172.50.50.1, 00:00:06, FastEthernet0/0
> > >
> > > r5#conf t
> > > Enter configuration commands, one per line. End with CNTL/Z.
> > > r5(config)#ip route 172.50.10.1 255.255.255.255 172.50.50.1
> > >
> > > 00:55:02: %BGP-5-ADJCHANGE: neighbor 172.50.10.1 Up bgp ev
> > >
> > > r5#sh ip bgp sum
> > > BGP router identifier 60.5.5.5, local AS number 55
> > > BGP table version is 1, main routing table version 1
> > >
> > > Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down
> > > State/PfxRcd
> > > 172.50.10.1 4 65 5 5 1 0
> 0 00:02:01
> > > 0
> > > r5# sh ip ro
> > > <snip>
> > >
> > > S 172.50.10.1/32 [1/0] via 172.50.50.1
> > > R* 0.0.0.0/0 [120/1] via 172.50.50.1, 00:00:13, FastEthernet0/0
> > >
> > > r5#
> > > router bgp 55
> > > bgp log-neighbor-changes
> > > neighbor 172.50.10.1 remote-as 65
> > > neighbor 172.50.10.1 ebgp-multihop 2
> > > r1#
> > > router bgp 65
> > > bgp log-neighbor-changes
> > > neighbor 172.50.50.5 remote-as 55
> > > neighbor 172.50.50.5 ebgp-multihop 2
> > >
> > > Thank You,
> > >
> > > Dmitry Volkov
> > > CCIE # 10292
> > >
> > >
> > >
> >
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