From: Kenneth Wygand (KWygand@customonline.com)
Date: Fri Apr 23 2004 - 12:36:12 GMT-3
Troy,
By including the "name" option, you are essentially telling the router
"To reach this IP address (specified in the map command), you must send
to (name here). Without the dialer string, there is no "name"
associated with the IP address to reach, so the router just sends
traffic out the dialing interface.
The reason your scenario doesn't work is because R2 doesn't know how to
reach R1 even though the BRI circuit is up. In order to have R2
recognize R1's name, R1 must tell R2 who it is. This is accomplished
through PPP Authentication (either PAP or CHAP). This builds the
Name-To-IP_Address mapping (like a static route) in R2.
You may now say, "Why would I include the "name" option in this scenario
if it only makes things more complicated? Well consider the following:
1) You specify the "name" option on both sides and enable authentication
so each side knows who each other is.
2) You configure both sides to be able to dial each other in case of
failure
Result: Only one side will initiate the connection. When the other side
attempts to initiate the connection, it will realize it is already
connected to the router it needs to reach (through the
Name-To-IP_Address mapping).
_However_, if you do _not_ use the name option and both sides can dial,
in the case of link failure, R1 will dial R2 when it sees interesting
traffic, and R2 will dial R1 in return when it sees interesting traffic
(because it doesn't know it's already connected to R1). Consequently,
both BRI circuits will come up, each dialed in opposite directions,
whenever interesting traffic is seen.
Hope this helps!
Kenneth E. Wygand
Systems Engineer, Project Services
CISSP #37102, CCNP, CCDP, ACSP, Cisco IPT Design Specialist, MCP, CNA,
Network+, A+
Custom Computer Specialists, Inc.
"The only unattainable goal is the one not attempted."
-Anonymous
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Troy
Sent: Friday, April 23, 2004 11:20 AM
To: ccielab@groupstudy.com
Subject: Dialer Map "name" parameter
All,
Can anyone explain what exactly the "name" keyword for the dialer map
statement is used for?
I know that you must have it for PPP callback. However I noticed that
including the keyword breaks a scenario that I would not think it would.
For example if you ONLY want one side of a BRI to dial. So you omit the
dialer string on the dialer map for the side that should NOT dial to
accomplish this. When the dialer map has the name keyword, but no dial
string, and an incoming call comes in, the connection is established but
there are encapsulation failures back towards the calling router.
If you do not use the name keyword then the scenario works fine. Anyone
know why this causes problems?
R1
dialer map ip 1.1.1.2 name R2 broadcast XXXXXXX
and
R2
dialer map ip 1.1.1.1 name R1 broadcast
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