From: Larry Metzger (larrymetzger@sbcglobal.net)
Date: Sat Aug 07 2004 - 23:45:07 GMT-3
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
>
>
This archive was generated by hypermail 2.1.4 : Fri Sep 03 2004 - 07:02:34 GMT-3