Godwin,
I'll try to answer your questions but I'm not sure I'll hit the
nail on the head:
#1) "Is it mean I can only WATCH a loopback address? Can I WATCH a
particular interface?"
You're not watching any type of interface with dialer-watch...you're
looking for the existence of a route in the routing table. If you
decide to watch a /32 route that's been learned it should work.
#2) "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"
Answer: You can watch the route for the network on which an Ethernet
interface resides--not if it's connected though. How/why would you get
a /32 route for an Ethernet interface into the routing table? If you
want the isdn to "back-up" the Ethernet interface, then watch a route
being learned through that interface. Be careful, if you're learning
via another interface also, dialer-watch won't dial.
Generally, if you're learning the route through a link (frame/PPP/HDLC
it doesn't matter) and the route disappears from the routing table (for
any reason) dialing should occur. Show dialer will provide the reason
"dialing on watched route loss" (or something like that.)
#3) "... 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?"
Answer: Again, it's not looking at the state of any interface. It's
looking for the existence of a route in the routing table. If you're
watching a router learned via the frame link and the DLCI stays up on
the A-side but the route disappears because the DLCI on the B-side goes
down; dialing will still take place although the state of the B-side
DLCI is unknown to router A. It's not a factor here.
Keep in mind...you have to make sure the router knows how to reach the
watched route via the DDR link or all you've accomplished is dialing.
While this may be cool it's not very useful. So in the scenarios you're
setting up to test this feature, make sure dialing restores the
connectivity lost when the watched route disappears (via routing
protocol, static route)
I sure hope this helps. Aloha, Frank
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
Godwin Pang
Sent: Monday, December 17, 2001 5:53 PM
To: [EMAIL PROTECTED]
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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