IS-IS,why would you use this vs. others

Discussion in 'Cisco' started by wysiwyg21, Feb 1, 2005.

  1. wysiwyg21

    wysiwyg21 Guest

    Just reading about IS-IS it appears to have limitations that other
    routing protocols don't have. In configurations over NBMA frame relay
    or dealing with suboptimal routes because of its static metric it does
    not appear to have the flexibility or richness that OSPF does. So, what
    are IS-IS benefits vs. the other protocols? I've read that IS-IS is
    used by ISPs. Why do they use it instead of others?
    wysiwyg21, Feb 1, 2005
    #1
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  2. wysiwyg21

    John Osmon Guest

    wysiwyg21 <> wrote:
    : Just reading about IS-IS it appears to have limitations that other
    : routing protocols don't have. In configurations over NBMA frame relay
    : or dealing with suboptimal routes because of its static metric it does
    : not appear to have the flexibility or richness that OSPF does. So, what
    : are IS-IS benefits vs. the other protocols? I've read that IS-IS is
    : used by ISPs. Why do they use it instead of others?

    For the most part, the choice between IS-IS and OSPF comes down to
    personal preference. I like IS-IS because it is *built* to carry metrics
    for protocols other than IPv4 (e.g. IPv6). Other people like OSPF
    becuase it runs over IPv4.

    Also, there are a number of useful pieces of equipment that will
    never speak IS-IS -- so OSPF might be the only choice available
    under certain circumstances.

    A good presentation on the subject can be found at:
    http://www.nanog.org/mtg-0006/katz.html
    John Osmon, Feb 2, 2005
    #2
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  3. wysiwyg21

    Ben Guest

    John Osmon wrote:
    > wysiwyg21 <> wrote:
    > : Just reading about IS-IS it appears to have limitations that other
    > : routing protocols don't have. In configurations over NBMA frame relay
    > : or dealing with suboptimal routes because of its static metric it does
    > : not appear to have the flexibility or richness that OSPF does. So, what
    > : are IS-IS benefits vs. the other protocols? I've read that IS-IS is
    > : used by ISPs. Why do they use it instead of others?
    >
    > For the most part, the choice between IS-IS and OSPF comes down to
    > personal preference. I like IS-IS because it is *built* to carry metrics
    > for protocols other than IPv4 (e.g. IPv6). Other people like OSPF
    > becuase it runs over IPv4.
    >
    > Also, there are a number of useful pieces of equipment that will
    > never speak IS-IS -- so OSPF might be the only choice available
    > under certain circumstances.
    >
    > A good presentation on the subject can be found at:
    > http://www.nanog.org/mtg-0006/katz.html

    great link
    Ben, Feb 2, 2005
    #3
  4. wysiwyg21

    Stephan Guest

    If you look at IS-IS vs. OSPF, than you will see that...



    - IS-IS is more flexible when extending the backbone.

    - IS-IS supports OSI and TCP/IP

    - IS-IS is more extensible through TLV (type, length, value) design



    Regards

    Stephan
    Stephan, Feb 2, 2005
    #4
  5. In article <>,
    wysiwyg21 <> wrote:
    >Just reading about IS-IS it appears to have limitations that other
    >routing protocols don't have. In configurations over NBMA frame relay
    >or dealing with suboptimal routes because of its static metric it does
    >not appear to have the flexibility or richness that OSPF does. So, what
    >are IS-IS benefits vs. the other protocols? I've read that IS-IS is
    >used by ISPs. Why do they use it instead of others?


    Every routing protocol makes trade offs, which means that each has
    its strengths and weaknesses. None are ideal for all applications.

    As for why IS-IS in ISPs, two factors which had a major influence
    at the time but no longer apply: IS-IS was available, stable,
    and functional years before OSPF could be trusted; and IS-IS could
    also be used to route OSI CLNS, which was considered a requirement
    for a while. If and when IPv6 routing becomes an issue, it will
    be interesting to see if history repeats itself, given that IS-IS
    merely needs a few minor tweaks to add IPv6 support to existing
    structures while OSPF is so IPv4 optimized it will need a rewrite.

    --
    Vincent C Jones, Consultant Expert advice and a helping hand
    Networking Unlimited, Inc. for those who want to manage and
    Tenafly, NJ Phone: 201 568-7810 control their networking destiny
    http://www.networkingunlimited.com
    Vincent C Jones, Feb 3, 2005
    #5
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