From: Larry Metzger (larrymetzger@sbcglobal.net)
Date: Sun Aug 08 2004 - 00:22:15 GMT-3
I stumbled onto this. I finished the lab and started going through the
Proctor Guide. I saw the "neighbor 150.50.17.2 update-source loopback
0" and thought "Damn I forgot one thing" Then I checked my BGP again to
see how that could be because everything was working. I put the command
in and checked (it looked exactly the same). I took it out and put it
back several times..... It has been running for about an hour without a
flap. Steady as a rock. I don't know if they changed something and
forgot to tell us or what.
Larry
-----Original Message-----
From: ccie2be [mailto:ccie2be@nyc.rr.com]
Sent: Saturday, August 07, 2004 8:13 PM
To: Larry Metzger; 'Group Study'
Subject: Re: BGP Update Source
Very interesting. Hopefully, one of the bgp guru's will chime in with
an
explanation for why this is happening.
All, I can say, is that in my limited bgp experience, if I didn't follow
the
rules exactly, things never worked.
I'll stayed tuned to this thread.
----- Original Message -----
From: "Larry Metzger" <larrymetzger@sbcglobal.net>
To: "'Group Study'" <ccielab@groupstudy.com>
Sent: Saturday, August 07, 2004 10:45 PM
Subject: RE: BGP Update Source
> I'll respond here for both CCIE2BE and William. If you're not into
BGP
> ignore this!!!!!
>
> I understand the concepts very well. However, I have to say that in
the
> lab it works as I have described and the following should show what I
am
> talking about.
>
> For those interested in a full network diagram...I'm using IPExpert
lab
> number 9 on BGP. I have a router R1 (1605 with 12.2(15)T13)
connecting
> over Ethernet to R2 (2503 with 12.2(24b)). The R1 has a loopback0 IP
> 200.0.0.1 that will be called as the neighbor by R2. R1 calls
neighbor
> using Ethernet address. WITH OR WITHOUT the update-source command
> connections are created and the systems work with BGP. What follows
is
> lengthy.
>
> hostname r1
> !
> interface Loopback0
> ip address 200.0.0.1 255.255.255.255
> !
> interface Ethernet0
> ip address 150.50.17.1 255.255.255.0
> !
> router bgp 100
> no synchronization
> bgp router-id 200.0.0.1
> bgp log-neighbor-changes
> network 192.168.10.0 mask 255.255.255.240
> network 192.168.10.16 mask 255.255.255.240
> network 192.168.20.32 mask 255.255.255.240
> network 192.168.20.48 mask 255.255.255.240
> aggregate-address 192.168.10.0 255.255.255.0 summary-only
> aggregate-address 192.168.20.0 255.255.255.0 summary-only
> neighbor 150.50.17.2 remote-as 200
> no auto-summary
> !
>
> r1#clear ip bgp *
> r1#
> *Mar 1 00:05:01.175: %BGP-5-ADJCHANGE: neighbor 150.50.17.2 Down User
> reset
> r1#
> *Mar 1 00:05:43.513: %BGP-5-ADJCHANGE: neighbor 150.50.17.2 Up
> r1#sh ip bgp nei
> BGP neighbor is 150.50.17.2, remote AS 200, external link
> BGP version 4, remote router ID 200.0.0.2
> BGP state = Established, up for 00:01:16
> Last read 00:00:15, hold time is 180, keepalive interval is 60
seconds
> Neighbor capabilities:
> Route refresh: advertised and received(old & new)
> Address family IPv4 Unicast: advertised and received
> Message statistics:
> InQ depth is 0
> OutQ depth is 0
> Sent Rcvd
> Opens: 2 2
> Notifications: 0 0
> Updates: 2 4
> Keepalives: 10 10
> Route Refresh: 0 0
> Total: 14 16
> Default minimum time between advertisement runs is 30 seconds
>
> For address family: IPv4 Unicast
> BGP table version 14, neighbor version 14
> Index 1, Offset 0, Mask 0x2
> Sent Rcvd
> Prefix activity: ---- ----
> Prefixes Current: 2 3 (Consumes 144 bytes)
> Prefixes Total: 2 3
> Implicit Withdraw: 0 0
> Explicit Withdraw: 0 0
> Used as bestpath: n/a 3
> Used as multipath: n/a 0
>
> Outbound Inbound
> Local Policy Denied Prefixes: -------- -------
> Bestpath from this peer: 3 n/a
> Suppressed due to dampening: 4 n/a
> Total: 7 0
> Number of NLRIs in the update sent: max 2, min 0
>
> Connections established 2; dropped 1
> Last reset 00:02:00, due to User reset
> Connection state is ESTAB, I/O status: 1, unread input bytes: 0
> Local host: 200.0.0.1, Local port: 179
> Foreign host: 150.50.17.2, Foreign port: 11003
>
> Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
>
> Event Timers (current time is 0x67EE8):
> Timer Starts Wakeups Next
> Retrans 7 0 0x0
> TimeWait 0 0 0x0
> AckHold 5 1 0x0
> SendWnd 0 0 0x0
> KeepAlive 0 0 0x0
> GiveUp 0 0 0x0
> PmtuAger 0 0 0x0
> DeadWait 0 0 0x0
>
> iss: 3216124146 snduna: 3216124336 sndnxt: 3216124336 sndwnd:
> 16195
> irs: 1986047258 rcvnxt: 1986047484 rcvwnd: 16159 delrcvwnd:
> 225
>
> SRTT: 182 ms, RTTO: 1073 ms, RTV: 891 ms, KRTT: 0 ms
> minRTT: 4 ms, maxRTT: 300 ms, ACK hold: 200 ms
> Flags: passive open, nagle, gen tcbs
> --More--
> Datagrams (max data segment is 536 bytes):
> Rcvd: 10 (out of order: 0), with data: 5, total data bytes: 225
> Sent: 8 (retransmit: 0, fastretransmit: 0), with data: 6, total data
> bytes: 189
> r1#sh ip bgp
> BGP table version is 14, local router ID is 200.0.0.1
> 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
> *> 10.1.1.0/24 150.50.17.2 0 200 300
310
> 320 330 i
> s> 192.168.10.0/28 0.0.0.0 0 32768 i
> *> 192.168.10.0 0.0.0.0 32768 i
> s> 192.168.10.16/28 0.0.0.0 0 32768 i
> *> 192.168.20.0 0.0.0.0 32768 i
> s> 192.168.20.32/28 0.0.0.0 0 32768 i
> s> 192.168.20.48/28 0.0.0.0 0 32768 i
> *> 200.0.0.4/32 150.50.17.2 0 200 300
310
> 320 330 i
> *> 200.0.0.6/32 150.50.17.2 0 200 i
> r1#sh tcp
>
> Stand-alone TCP connection from host 150.50.17.2
> Connection state is ESTAB, I/O status: 1, unread input bytes: 0
> Local host: 200.0.0.1, Local port: 179
> Foreign host: 150.50.17.2, Foreign port: 11003
>
> Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
>
> Event Timers (current time is 0x69CCC):
> Timer Starts Wakeups Next
> Retrans 7 0 0x0
> TimeWait 0 0 0x0
> AckHold 5 1 0x0
> SendWnd 0 0 0x0
> KeepAlive 0 0 0x0
> GiveUp 0 0 0x0
> PmtuAger 0 0 0x0
> DeadWait 0 0 0x0
>
> iss: 3216124146 snduna: 3216124336 sndnxt: 3216124336 sndwnd:
> 16195
> irs: 1986047258 rcvnxt: 1986047484 rcvwnd: 16159 delrcvwnd:
> 225
>
> SRTT: 182 ms, RTTO: 1073 ms, RTV: 891 ms, KRTT: 0 ms
> minRTT: 4 ms, maxRTT: 300 ms, ACK hold: 200 ms
> Flags: passive open, nagle, gen tcbs
>
> Datagrams (max data segment is 536 bytes):
> Rcvd: 10 (out of order: 0), with data: 5, total data bytes: 225
> Sent: 8 (retransmit: 0, fastretransmit: 0), with data: 6, total data
> bytes: 189
> r1#
> *************************************************
> hostname r2
> !
> interface Ethernet0
> ip address 150.50.17.2 255.255.255.0
> !
> router bgp 65256
> no synchronization
> bgp router-id 200.0.0.2
> bgp log-neighbor-changes
> bgp confederation identifier 200
> bgp confederation peers 65078
> neighbor 150.50.24.4 remote-as 300
> neighbor 150.50.24.4 route-map task11 out
> neighbor 150.50.100.5 remote-as 65256
> neighbor 150.50.100.5 next-hop-self
> neighbor 150.50.100.5 route-map task10 out
> neighbor 200.0.0.1 remote-as 100
> neighbor 200.0.0.1 ebgp-multihop 2
> no auto-summary
> !
> ip route 200.0.0.1 255.255.255.255 150.50.17.1
>
>
> sh ip bgp nei 200.0.0.1
> BGP neighbor is 200.0.0.1, remote AS 100, external link
> BGP version 4, remote router ID 200.0.0.1
> BGP state = Established, up for 00:02:07
> Last read 00:00:08, hold time is 180, keepalive interval is 60
seconds
> Neighbor capabilities:
> Route refresh: advertised and received(old & new)
> Address family IPv4 Unicast: advertised and received
> Message statistics:
> InQ depth is 0
> OutQ depth is 0
> Sent Rcvd
> Opens: 2 2
> Notifications: 0 0
> Updates: 4 2
> Keepalives: 11 11
> Route Refresh: 0 0
> Total: 17 15
> Default minimum time between advertisement runs is 30 seconds
>
> For address family: IPv4 Unicast
> BGP table version 12, neighbor version 12
> Index 3, Offset 0, Mask 0x8
> Sent Rcvd
> Prefix activity: ---- ----
> Prefixes Current: 3 2 (Consumes 72 bytes)
> Prefixes Total: 3 2
> Implicit Withdraw: 0 0
> Explicit Withdraw: 0 0
> Used as bestpath: n/a 2
> Used as multipath: n/a 0
>
> Outbound Inbound
> Local Policy Denied Prefixes: -------- -------
> Well-known Community: 2 n/a
> Bestpath from this peer: 2 n/a
> Total: 4 0
> Number of NLRIs in the update sent: max 2, min 0
>
> Connections established 2; dropped 1
> Last reset 00:02:49, due to Peer closed the session
> External BGP neighbor may be up to 2 hops away.
> --More-- Connection state is ESTAB, I/O
> status: 1, unread input bytes: 0
> Local host: 150.50.17.2, Local port: 11003
> Foreign host: 200.0.0.1, Foreign port: 179
>
> Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
>
> Event Timers (current time is 0x87ED4):
> Timer Starts Wakeups Next
> Retrans 7 0 0x0
> TimeWait 0 0 0x0
> AckHold 7 4 0x0
> SendWnd 0 0 0x0
> KeepAlive 0 0 0x0
> GiveUp 0 0 0x0
> PmtuAger 0 0 0x0
> DeadWait 0 0 0x0
>
> iss: 1986047258 snduna: 1986047503 sndnxt: 1986047503 sndwnd:
> 16140
> irs: 3216124146 rcvnxt: 3216124355 rcvwnd: 16176 delrcvwnd:
> 208
>
> SRTT: 182 ms, RTTO: 1073 ms, RTV: 891 ms, KRTT: 0 ms
> minRTT: 8 ms, maxRTT: 300 ms, ACK hold: 200 ms
> Flags: higher precedence, nagle
> --More--
> Datagrams (max data segment is 536 bytes):
> Rcvd: 10 (out of order: 0), with data: 7, total data bytes: 208
> Sent: 12 (retransmit: 0, fastretransmit: 0), with data: 6, total data
> bytes: 244
> r2#sh ip bgp
> BGP table version is 12, local router ID is 200.0.0.2
> 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
> *>i8.8.8.0/24 150.50.100.5 0 100 0 (65078) ?
> *> 10.1.1.0/24 150.50.24.4 0 0 300 310
320
> 330 i
> *>i150.50.4.0/24 150.50.100.5 20 100 0 (65078) ?
> *> 192.168.10.0 200.0.0.1 0 0 100 i
> *> 192.168.20.0 200.0.0.1 0 0 100 i
> *> 200.0.0.4/32 150.50.24.4 0 0 300 310
320
> 330 i
> *>i200.0.0.6/32 150.50.100.6 0 100 0 i
> r2#sh tcp
>
> Stand-alone TCP connection to host 150.50.100.5
> Connection state is ESTAB, I/O status: 1, unread input bytes: 0
> Local host: 150.50.100.2, Local port: 11000
> Foreign host: 150.50.100.5, Foreign port: 179
>
> Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
>
> Event Timers (current time is 0x8A168):
> Timer Starts Wakeups Next
> Retrans 16 0 0x0
> TimeWait 0 0 0x0
> AckHold 10 6 0x0
> SendWnd 0 0 0x0
> KeepAlive 0 0 0x0
> GiveUp 0 0 0x0
> PmtuAger 0 0 0x0
> DeadWait 0 0 0x0
>
> iss: 3993375966 snduna: 3993376441 sndnxt: 3993376441 sndwnd:
> 15910
> irs: 1772481955 rcvnxt: 1772482393 rcvwnd: 15947 delrcvwnd:
> 437
>
> SRTT: 265 ms, RTTO: 545 ms, RTV: 280 ms, KRTT: 0 ms
> --More-- minRTT: 8 ms, maxRTT: 308 ms, ACK
> hold: 200 ms
> Flags: higher precedence, nagle
>
> Datagrams (max data segment is 1460 bytes):
> Rcvd: 19 (out of order: 0), with data: 10, total data bytes: 437
> Sent: 23 (retransmit: 0, fastretransmit: 0), with data: 15, total data
> bytes: 474
>
> Stand-alone TCP connection to host 200.0.0.1
> Connection state is ESTAB, I/O status: 1, unread input bytes: 0
> Local host: 150.50.17.2, Local port: 11003
> Foreign host: 200.0.0.1, Foreign port: 179
>
> Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
>
> Event Timers (current time is 0x8AA78):
> Timer Starts Wakeups Next
> Retrans 7 0 0x0
> TimeWait 0 0 0x0
> AckHold 7 4 0x0
> SendWnd 0 0 0x0
> KeepAlive 0 0 0x0
> GiveUp 0 0 0x0
> --More-- PmtuAger 0 0
> 0x0
> DeadWait 0 0 0x0
>
> iss: 1986047258 snduna: 1986047503 sndnxt: 1986047503 sndwnd:
> 16140
> irs: 3216124146 rcvnxt: 3216124355 rcvwnd: 16176 delrcvwnd:
> 208
>
> SRTT: 182 ms, RTTO: 1073 ms, RTV: 891 ms, KRTT: 0 ms
> minRTT: 8 ms, maxRTT: 300 ms, ACK hold: 200 ms
> Flags: higher precedence, nagle
>
> Datagrams (max data segment is 536 bytes):
> Rcvd: 10 (out of order: 0), with data: 7, total data bytes: 208
> Sent: 12 (retransmit: 0, fastretransmit: 0), with data: 6, total data
> bytes: 244
>
> Stand-alone TCP connection to host 150.50.24.4
> Connection state is ESTAB, I/O status: 1, unread input bytes: 0
> Local host: 150.50.24.2, Local port: 11001
> Foreign host: 150.50.24.4, Foreign port: 179
>
> Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
>
> Event Timers (current time is 0x8B298):
> Timer Starts Wakeups Next
> --More-- Retrans 13 0
> 0x0
> TimeWait 0 0 0x0
> AckHold 12 7 0x0
> SendWnd 0 0 0x0
> KeepAlive 0 0 0x0
> GiveUp 0 0 0x0
> PmtuAger 0 0 0x0
> DeadWait 0 0 0x0
>
> iss: 2325565762 snduna: 2325566044 sndnxt: 2325566044 sndwnd:
> 16103
> irs: 1896377811 rcvnxt: 1896378110 rcvwnd: 16086 delrcvwnd:
> 298
>
> SRTT: 253 ms, RTTO: 657 ms, RTV: 404 ms, KRTT: 0 ms
> minRTT: 24 ms, maxRTT: 404 ms, ACK hold: 200 ms
> Flags: higher precedence, nagle
>
> Datagrams (max data segment is 1460 bytes):
> Rcvd: 18 (out of order: 0), with data: 12, total data bytes: 298
> Sent: 21 (retransmit: 0, fastretransmit: 0), with data: 12, total data
> bytes: 281
> r2
>
> -----Original Message-----
> From: William Chen [mailto:kwchen@netvigator.com]
> Sent: Saturday, August 07, 2004 7:07 PM
> To: Larry Metzger; Group Study
> Subject: Re: BGP Update Source
>
> Hi Larry,
>
> I think update-source is necessary, if you want to form the BGP
peer
> using loopback address. It is because, when BGP get reply from
neighbor,
> it
> will expected the source address of the reply is matching with the
> address
> you set in the neighbor statement. It is impossible that the reply
> message
> from the BGP peer use loopback as source address (it will use the
> outging
> physical address as the source address for most time), unless you told
> the
> router to do so (i.e. using the update-source command).
>
> I will appreciate if you send us the configuration and also state
> which
> IOS version you used.
>
> HTH,
> William
>
> ----- Original Message -----
> From: "Larry Metzger" <larrymetzger@sbcglobal.net>
> To: "Group Study" <ccielab@groupstudy.com>
> Sent: Sunday, August 08, 2004 8:10 AM
> Subject: BGP Update Source
>
>
> > I am working on BGP configurations. I have Router1 (as100) and
> Router2
> > (as200). I'm using the loopback on Router1 for the neighbor
> statement.
> > The recommendation is to add "neigh R2 update-source loop0" I have
> > configured these routers with and without the update source and
> > everything works fine either way (sh ip bgp, sh ip bgp nei, sh tcp).
> Is
> > it necessary? What problems will it cause if you don't change the
> > update-source?
> >
> > Larry
> >
> >
>
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