From: Chris Allen (chris.allen@xxxxxxxxxxxx)
Date: Tue Dec 18 2001 - 13:44:56 GMT-3
Question 1: You have to watch a network that it listed in the "watching"
routers routing table. So for you example you could watch the RtB Ethernet
IP address if RtA has that /32 route in it's routing table. On normal
circumstances it would not but you could add a static route on RtB and
propagate it to RtA??? Not clean or recommended but it would work.
Question 2: Frame Relay and Dialer Watch (or Dial period)
The problem with frame relay is that some frame networks out there still do
not use A-bit Notification. A-bit Notification is simply a mechanism to
notify the opposite end of a frame PVC that there is an outage. Without
A-bit Notification, one end of a Frame PVC could essentially be down and the
other would still be receiving LMI and appear as up up. Therefore if the
router is watching the PVC subnet and the interface doesn't go down, the
route will not be removed from the routing table and the router will not
dial. The best thing to do to counter this is, find out from your provider
if your PVC's utilize A-bit notification. If your provider does not and can
not support A-bit then configure end-to-end keepalives on your routers, this
will due the same thing as A-bit, but the communication will be between the
routers instead of the frame switches.
Chris
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Godwin Pang
Sent: 18 December 2001 06:53
To: ccielab@groupstudy.com
Subject: Dialer watch question
Hi Group,
Please help me to understand Dialer watch.
Quoted from the document
http://www.cisco.com/warp/public/129/bri-backup-map-watch.html
"When a watched route is deleted, dialer watch checks for at least one valid
route for any of the IP addresses or networks being watched. "
"dialer watch-list group-number ip ip-address address-mask : Defines the IP
addresses or networks to be watched. The address or network (with the
correct mask) that is configured must exist in the routing table. "
I think the first quote said I can backup a particular ip address with
dialer watch, while the second one said the ip address with the mask must be
in the routing table.
However, except loopback interface, I seldom see any ip address (with /32
mask) in the routing table. Is it mean I can only WATCH a loopback address?
Can I WATCH a particular interface?
For example: Imagine there is an isdn link between Router A and Router B
-------------e0-Router_A-S0--------------------------S0-Router_B-e0------
-------------
10.1.1.0/24 11.1.1.0/24
12.1.1.0/24
Can I use dialer watch to WATCH the ethernet interface address of Router B?
e.g. dialer watch-list 1 ip 12.1.1.1 255.255.255.255
Another question
Quoted from the document
http://www.cisco.com/warp/public/123/backup-main.html
"Dialer Watch does not rely on interesting packets to trigger dialing. The
link is automatically brought up when the primary route goes down without
postponing dialing. This is an important consideration on Frame Relay
circuits, where the line protocol may not go down if the DLCI is inactive. "
Assume the connection between Router A and Router B is FR, is it mean that
dialer watch will not dial if the watched network is 11.1.1.0/24 because the
DLCI of Router A is still up even the S0 of Router B is down?
I know the solution is to watch the 12.1.1.0 network, but will it dial if I
WATCH the ip address of router B's S0?
Thanks,
Godwin
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