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475 Views 3 Replies Latest reply: May 3, 2012 9:24 PM by Martin RSS

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Hello packets.

May 3, 2012 10:54 AM

Matt 37 posts since
Nov 16, 2011

I have never understood what hello packets are. I know OSPF and EIGRP routers will establish adjacencies through hello packets. Can Somebody explain what they are? Thanks. Matt

  • Martin 13,077 posts since
    Jan 16, 2009
    Currently Being Moderated
    1. May 3, 2012 11:48 AM (in response to Matt)
    Re: Hello packets.

    hello packets have appropriate info for two neighboring routers to become neighbors and exchange routes; Routers receive hello packet and compare their fields; if specific values are match, routers agree on becoming neighbors and start exchange routes.

     

    EIGRP will include IP address, K values, AS number, and some other info.

     

    OSPF have Area number and mtu besides the IP address, plus other info;

     

    W.Odom in CCNA book has nice table with values in hello packets and which ones have to match.

  • Martin 13,077 posts since
    Jan 16, 2009
    Currently Being Moderated
    3. May 3, 2012 9:24 PM (in response to Matt)
    Re: Hello packets.

    you are welcome

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