Load Balancing and EIGRP

Discussion in 'Cisco' started by Manoj Kumar Reddy, Dec 25, 2003.

  1. Hi Guys,

    i got a questions regarding loadbalancing on Cisco routers. say, I
    have two locations( SiteA and SiteB) connected by two E1(LinkA, LinkB
    of equal cost) Links and i am using load balancing on these two links.
    i am using VoIP between Site A and Site B,so voice packets are also
    routed via these two links. its everything ok if these two links are
    stable. what happens when one of the links(say Link A) is
    inconsistent. I mean if the LinkA is going up and down very frequently
    ( say for every 30 seconds), what happens to the voice packets?can the
    packets that are routed on Link A reach their destination? i suppose,
    if the packets are lost on link A, i can't ask the speaker to
    reproduce the packets like how data packets are regenerated by their
    applications, if they are lost. I think IOS maintains the route
    corresponding to failed link for some period of time in its routing
    table. what happenes to the voice packets routed via this particular
    link A in the time between the link failure and the time of deletion
    of route by IOS from its routing table?

    how the IOS behaves in this situation and how the packets are routed
    to destination and still using loadbalancing and EIGRP? how can I do
    this?

    any one plz help me.

    regards
    Manoj.
    Manoj Kumar Reddy, Dec 25, 2003
    #1
    1. Advertising

  2. Manoj Kumar Reddy

    shope Guest

    "Manoj Kumar Reddy" <> wrote in message
    news:...
    > Hi Guys,
    >
    > i got a questions regarding loadbalancing on Cisco routers. say, I
    > have two locations( SiteA and SiteB) connected by two E1(LinkA, LinkB
    > of equal cost) Links and i am using load balancing on these two links.
    > i am using VoIP between Site A and Site B,so voice packets are also
    > routed via these two links. its everything ok if these two links are
    > stable. what happens when one of the links(say Link A) is
    > inconsistent.


    Basically you are now running the most sensitive error detection protocol in
    common use on a packet network (voip) - consistant packet loss, topology
    changes etc will cause quality problems with voip before any conventional
    data traffic problems show up.

    I mean if the LinkA is going up and down very frequently
    > ( say for every 30 seconds), what happens to the voice packets?can the
    > packets that are routed on Link A reach their destination?


    No - you have a "black hole" - packets sent that way are never seen again.

    i suppose,
    > if the packets are lost on link A, i can't ask the speaker to
    > reproduce the packets like how data packets are regenerated by their
    > applications, if they are lost. I think IOS maintains the route
    > corresponding to failed link for some period of time in its routing
    > table.


    EIGRP runs recalcs on an event, but with a delay to dampen the number of
    changes found

    what happenes to the voice packets routed via this particular
    > link A in the time between the link failure and the time of deletion
    > of route by IOS from its routing table?


    Gone.

    You may want to look at LQM which can measure the reliability of a link and
    take it out of service if it falls below a threshold.
    http://www.cisco.com/en/US/products...ation_guide_chapter09186a008008730a.html#3911
    >
    > how the IOS behaves in this situation and how the packets are routed
    > to destination and still using loadbalancing and EIGRP? how can I do
    > this?


    I dont think EIGRP is the issue - the same stuff happens with any routing
    protocol, in that some kinds of faults depend on a timeout, so there is a
    delay between a fault and detection of a fault.
    >
    > any one plz help me.
    >
    > regards
    > Manoj.

    --
    Regards

    Stephen Hope - remove xx from email to reply
    shope, Dec 25, 2003
    #2
    1. Advertising

  3. Manoj Kumar Reddy

    phase90 Guest

    Manoj,

    This issue came up last week on ccie groupstudy. There is a
    mechanism

    that you may want to take a look at called ip event dampening. Click below
    to

    learn about it.

    http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guid
    e09186a0080110bc8.html

    I did not look very deeply into it but it looks like you can tune yout
    routing protocol

    to only install the route into the routing table if the interface is
    well-behaved.

    Good luck. Please let me know if this helps.


    Jerry

    "Manoj Kumar Reddy" <> wrote in message
    news:...
    > Hi Guys,
    >
    > i got a questions regarding loadbalancing on Cisco routers. say, I
    > have two locations( SiteA and SiteB) connected by two E1(LinkA, LinkB
    > of equal cost) Links and i am using load balancing on these two links.
    > i am using VoIP between Site A and Site B,so voice packets are also
    > routed via these two links. its everything ok if these two links are
    > stable. what happens when one of the links(say Link A) is
    > inconsistent. I mean if the LinkA is going up and down very frequently
    > ( say for every 30 seconds), what happens to the voice packets?can the
    > packets that are routed on Link A reach their destination? i suppose,
    > if the packets are lost on link A, i can't ask the speaker to
    > reproduce the packets like how data packets are regenerated by their
    > applications, if they are lost. I think IOS maintains the route
    > corresponding to failed link for some period of time in its routing
    > table. what happenes to the voice packets routed via this particular
    > link A in the time between the link failure and the time of deletion
    > of route by IOS from its routing table?
    >
    > how the IOS behaves in this situation and how the packets are routed
    > to destination and still using loadbalancing and EIGRP? how can I do
    > this?
    >
    > any one plz help me.
    >
    > regards
    > Manoj.
    phase90, Dec 26, 2003
    #3
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. David
    Replies:
    0
    Views:
    2,469
    David
    Nov 12, 2003
  2. JSA

    EIGRP load balancing

    JSA, Aug 10, 2004, in forum: Cisco
    Replies:
    7
    Views:
    9,273
    Ivan Ostres
    Aug 11, 2004
  3. MJ

    EIGRP and load balancing

    MJ, Mar 23, 2005, in forum: Cisco
    Replies:
    0
    Views:
    535
  4. Replies:
    1
    Views:
    2,268
    Vincent C Jones
    Nov 21, 2005
  5. James

    EIGRP load balancing

    James, Feb 11, 2007, in forum: Cisco
    Replies:
    4
    Views:
    569
    James
    Feb 12, 2007
Loading...

Share This Page