RE: NEWBIE -- Help on Configuring backup link

From: Wortendyke, Ken (KWortendyke@Timebridge.com)
Date: Mon Oct 22 2001 - 22:46:32 EDT


Like most environments, you've got lots of choices available for dial
back-up.

I haven't done these in a bit, but you'll want to review your requirements
if running a dynamic routing protocol over the ISDN link, whether you'll
need the ISDN line available for inbound/outbound for other sites, PPP
authentication mechanics, fine tuning your dialer list, and other ISDN-line
and PPP specific configuration issues (switch type, SPIDs, whether you'll
need two dialer maps or not, load thresholds, etc...).

Not reviewing the ISDN specific configuration commands, here's a basic
sample utilizing floating static routes, CHAP, and the back-up interface
command:
username <remote hostname> password <secret>
!
interface serial 0
  ip address n.n.n.h 255.255.255.m
  backup interface bri0
  backup delay <activation delay in seconds> <fallback delay in seconds>
!
interface bri0
  ip address n.n.n.h 255.255.255.m
  encapsulation ppp
  dialer map ip n.n.n.h name <remote hostname> <dialed number> broadcast
  dialer-group 1
  ppp authentication chap
  ppp multilink
!
!
ip route 0.0.0.0/0 serial0 !this is the primary default route over the
serial link
ip route 0.0.0.0/0 n.n.n.h 240 !this points to your ISP's ISDN interface
!
dialer-list 1 protocol ip permit
!

This really utilizes two techniques in one. You don't necessarily need both
the backup interface commands and the FSR. FSR fits better if you just run
a default static (or a couple of statics) over the primary link. Backup
interfaces are fairly simple to implement when you'll be running dynamic
protocols over both the primary and ISDN links. Although FSR could work if
your floating static route replaces a network learned dynamically, there
normally are other issues with dynamic protocols depending upon which one
you use.

Anyone else with suggestions?

HTH,
Ken W

-----Original Message-----
From: Suryadevara Venkata Raghava Rao [mailto:sukrith@www.com]
Sent: Monday, October 22, 2001 3:55 PM
To: cisco-nsp@puck.nether.net
Subject: NEWBIE -- Help on Configuring backup link

Hi Every One,

We are trying to configure a ISDN backup for a leasedline(sync-dedicated).
When ever the leased is down ISDN should dial automatically and get
connected to an ISP and should disconnect by itself when ever leased line
comes up.

Help is appreciated.

Thanks in Advance.

REgards
Venkat

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