Skip navigation
Cisco Learning Home > CCNP R&S Study Group > Discussions
3023 Views 9 Replies Latest reply: Feb 10, 2011 11:03 PM by smsnaqvi RSS

Currently Being Moderated

EIGRP link bandwith.

Feb 9, 2011 12:56 AM

Rizik 166 posts since
Jan 6, 2010

Hi everyone.

 

Can i change bandwith settings of serial link between two eigrp enabled routers, for example one side 768 kbs, other side 256kbs. Will there occur any prblems?

 

Regards

Rizik

  • Marko Milivojevic 800 posts since
    Jun 26, 2008
    Currently Being Moderated
    1. Feb 9, 2011 4:02 AM (in response to Rizik)
    Re: EIGRP link bandwith.

    You can change it, yes. Will there be any problems really depends on what you define as a problem :-).

     

    Note that changing bandwidth to tweak EIGRP metric is rather crude method, as EIGRP will carry only the lowest bandwidth on the path. Changing the bandwidth on that link may or may not affect the total metric. Changing "delay" parameter on interfaces is more convenient, as delay is cumulative.

     

    --

    Marko Milivojevic - CCIE #18427 (SP R&S)

    Senior Technical Instructor - IPexpert

  • Abzal 11 posts since
    Jan 29, 2011
    Currently Being Moderated
    3. Feb 9, 2011 1:07 PM (in response to Rizik)
    Re: EIGRP link bandwith.

    Heelo Rizik

    Yes Marko is right. Bandwidth it's a actully speed of the link. And delay it's a logical speed, so that you could change it.

  • Marko Milivojevic 800 posts since
    Jun 26, 2008
    Currently Being Moderated
    4. Feb 9, 2011 1:31 PM (in response to Abzal)
    Re: EIGRP link bandwith.

    Well.. Yes and no :-). Networks are a complex beasts :-).

     

    Bandwidth as used by EIGRP is actually logical bandwidth, determined by either default interface bandwidth, which is only in some cases derived from the actual "speed" of the interface, or by configured "bandwidth" statement on the interface itself.

     

    Delay on the other hand is just a pre-determined value for different interface types (it's not in any way measured), that can be modified using "delay" interface-level command.

     

    --

    Marko Milivojevic - CCIE #18427 (SP R&S)

    Senior Technical Instructor - IPexpert

  • Abzal 11 posts since
    Jan 29, 2011
    Currently Being Moderated
    5. Feb 9, 2011 9:31 PM (in response to Rizik)
    Re: EIGRP link bandwith.

    Yes, again you're  right Marko. When I said delay, I meant bandwidth as logical, and clock rate as actually speed. My bad. Cisco recommends change delay instead bandwidth, yes? :-)

  • Brian 2,968 posts since
    Aug 17, 2009
    Currently Being Moderated
    7. Feb 10, 2011 1:51 AM (in response to Rizik)
    Re: EIGRP link bandwith.

    Aloha Rizik,

     

    You can do this and you will affect the metric that each router calculates to get to the other router.   Here is a link to a similar discusion where ssetbob7 brought up the same issue.

     

    https://learningnetwork.cisco.com/message/124642#124642

     

    Take this basic setup:

     

    LAN 1 <--- 100M ---> R1 <----- serial -----> R2 <--- 100M ---> LAN 2

    LAN 1 = 192.168.1.0/24
    LAN 2 = 192.168.2.0/24
    100M Ethernet delay = 100 microseconds
    serial port delay = 20000 microseconds

     

    Configure 768kbps on the R1 side of the serial link and 256kbps on the R2 side.  What bandwidth will be used by each router to calculate their  metric to each other LAN subnets?

     

    R1 will use a bandwidth of 768 and a delay of 20100 microseconds for a metric of 3847680

     

    R2 will use a bandwidth of 256 and a delay of 20100 microseconds for a metric of 10514432

     

    I will leave you to setting this up in either PT, GNS3 or real equipment to verify.  So, yes you can configure each side to be different, but "why?" would you want to do this?

     

    HTH

  • smsnaqvi 533 posts since
    Feb 6, 2010
    Currently Being Moderated
    9. Feb 10, 2011 11:03 PM (in response to Rizik)
    Re: EIGRP link bandwith.

    Hi All

     

    In NBMA networks you have to make sure that the logical bandwidth does not exceed CIR, as the default on the serial lines are set to 1544kbps.

     

    Regards

Actions

More Like This

  • Retrieving data ...

Bookmarked By (0)