From: Omer Ansari (omer@xxxxxxxxxx)
Date: Sun Jun 30 2002 - 20:07:47 GMT-3
All,
33.1/16--[lo10](Rtr1)[bri0/0]---{isdn_cloud}--[bri0/0](Rtr2)
config snippets at the end of the email.
using legacy snapshot routing, with Rtr1 as client, and Rtr2 as server.
note that my quiet time is 8 min. and active time is 5min. that
essentially means, I am not going to have 33.1/16 for more than 3.5
minutes in Rtr2's routing table. (3 minutes of quiet time since last RIP
update in the activetime + max 30 seconds for last RIP update in active
time)
problem happens when I shut down lo0 (33.1/16) on Rtr1.
RIP does not make any effort in telling the other side if 33.1/16 is down
and is completely out of the Rtr1's routing table.
thus all it sends during the Next active time is:
*Mar 4 00:07:49.074: RIP: sending v1 update to 255.255.255.255 via BRI0/0
(12.0.1.1)
*Mar 4 00:07:49.074: RIP: build update entries - suppressing null update
meanwhile, R2, since it never got an [33.0.0.0 in 16 hops (inaccessible)]
update (that it WOULD have received if Rtr1 had atleast one more route to
tell rtr2 about) happily thinks it still has a route to 33.1/16 via Rtr1:
R2#
R2#sh ip route rip
R 33.0.0.0/8 [120/1] via 12.0.1.1, 00:11:03, BRI0/0
R2#
note: its 11+minutes since the last update.
So the questions are:
1. is this a corner case/ weakness of snapshot routing for RIP? or am I
missing something?
2. is there _any_ expiry timer for snapshot routes in case the router
responsible for sending the updates for those routes is having problems
communicating their down status?
If not, Rtr2 could keep the route indefinitely if Rtr1 is having problems
sending its updates to Rtr2 (say b/c of encapsulation failure)
thanks in advance!
Omer
Rtr1:
-----
!
interface BRI0/0
ip address 12.0.1.1 255.255.255.0
encapsulation ppp
no ip route-cache cef
dialer idle-timeout 60
dialer map snapshot 10 broadcast 4724821
dialer map ip 12.0.1.2 broadcast 4724821
dialer-group 1
isdn switch-type basic-ni
isdn spid1 919472482200 4724822
snapshot client 5 8 suppress-statechange-update dialer
ppp authentication chap
end
!
dialer-list 1 protocol ip permit
!
router rip
network 12.0.0.0
network 33.0.0.0
!
Rtr2:
-----
!
interface BRI0/0
ip address 12.0.1.2 255.255.255.0
encapsulation ppp
no ip route-cache
no ip mroute-cache
dialer idle-timeout 300
dialer map ip 12.0.1.1 broadcast 4724822
dialer-group 1
isdn switch-type basic-5ess
snapshot server 5 dialer
ppp authentication chap callin
end
!
dialer-list 1 protocol ip permit
!
router rip
network 12.0.0.0
!
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:36:15 GMT-3