Solved

Cisco Serial I/F Delay. Why is it lower on a single T-1 than multilinked T-1s?

Posted on 2003-10-30
4
316 Views
Last Modified: 2010-04-17
I configured two 7206s at a remote site, set them up with HSRP and then multilinked 3 T-1s to the hub site for router A and configured a single T-1 to the hub site on router B. Then I noticed that all of the remote site LAN traffic hopped from router A to router B and rode the single T-1 to the hub site . . .

Then I noticed that the delay on "show int" for the multilink was 100000, and for each single T-1 that was part of the multilink it was 20000. This was why EIGRP was saying that the preferred route was via router B, because as a single T-1 the delay was 20000, but showing 100000 over the multilink.

Anybody know what's going on here? Is "delay" a measured or calculated value?

Thanks,
Steve
0
Comment
Question by:SteveJ
4 Comments
 
LVL 7

Accepted Solution

by:
NicBrey earned 63 total points
Comment Utility
In stead of multilink, rather use CEF.  PPP multilink requires each packet to be process switched, CEF use fast switching. That is probably why you see more delay on the multilinked T1s.  
http://www.cisco.com/en/US/tech/tk827/tk831/technologies_tech_note09186a0080094806.shtml

Also not exatcly sure how the Delay is worked out. It's not specified in the EIGRP white paper either...
I think it is measured, but then some more calulations are made to get the final value that the router will use to calculate the metric of a route.
White paper:
http://www.cisco.com/en/US/tech/tk365/tk207/technologies_white_paper09186a0080094cb7.shtml#metrics
0
 
LVL 5

Assisted Solution

by:epylko
epylko earned 62 total points
Comment Utility
It sounds like your multilink is misconfigured. It shouldn't be possible to have traffic going over 1 T1 since you wouldn't have IP addresses on the individual T1 links. Post your config so we can take a look at it.

Also, PPP multilink is not and should not be process switched unless you are using a sufficiently old version of IOS. Some newer technologies like MLPPP over ATM (12.2-ish) has bugs where it process switches incoming MLPPP, but it looks like those bug fixes have been commited.

Finally, if you don't like the delay, change it with the "delay" interface command.  That's the best way to tweak EIGRP parameters, although you could use the bandwidth parameter too.

-Eric
0

Featured Post

How to run any project with ease

Manage projects of all sizes how you want. Great for personal to-do lists, project milestones, team priorities and launch plans.
- Combine task lists, docs, spreadsheets, and chat in one
- View and edit from mobile/offline
- Cut down on emails

Join & Write a Comment

In this tutorial I will show you with short command examples how to obtain a packet footprint of all traffic flowing thru your Juniper device running ScreenOS. I do not know the exact firmware requirement, but I think the fprofile command is availab…
Getting hacked is no longer a matter or "if you get hacked" — the 2016 cyber threat landscape is now titled "when you get hacked." When it happens — will you be proactive, or reactive?
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

728 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

14 Experts available now in Live!

Get 1:1 Help Now