Classful vs Classless Routing Protocol

walid97walid97 Member Posts: 79 ■■□□□□□□□□

I know that RIP1 and IGRP are classful protocols.. with classful can we use subnetting like using, or it should be only class B networks(as example)? (172.16 is class B).

If we can use do we type:
"Router(config-router)#Network" for both interfaces or, and for interface 1 and 2 respectively?

If we can use these 2 networks, can we go further and use different subnets in RIP1 and IGRP (VLSM) and let these protocols determine the subnet?

What about RIP2 (which is classless) do we type Network or both and ?? (this is classB subnetted /24)

Now about static routing, we type:
"Router(config)# ip route"
in static routing, can VLSM be used, that is different subnets?? because the Mask is included in the configuration, so I don't see why VLSM cant be used here.

thanks a lot !


  • rossonieri#1rossonieri#1 Member Posts: 799 ■■■□□□□□□□
    classful : =
    classles : = ( ex. only )
    the More I know, that is more and More I dont know.
  • walid97walid97 Member Posts: 79 ■■□□□□□□□□
    Well, in the Sybex book I found out that we must use for IGRP AND EIGRP:

    for a router that has 2 subnets ( and

    dunno I am confused here !
  • rossonieri#1rossonieri#1 Member Posts: 799 ■■■□□□□□□□
    your book saying that if you have 2 different subnet on your network : and then you would configure your igrp as network that is because igrp is classful routing protocol.
    but if you want to use eigrp then you would enable the ip classles command ; and enter those 2 network separately as +
    the More I know, that is more and More I dont know.
  • walid97walid97 Member Posts: 79 ■■□□□□□□□□
    No dude, I am sure of it.. it is EIGRP.. it in on the Sybex CCNA book, page 300.

    a router has 3 interfaces with:, and

    the configuration is:
    R(config)# router eigrp 100
    R(config-router)# network

    so eventhough EIGRP is classless, it used a classfull notation.
    is this a mistake !
  • DrakonblaydeDrakonblayde Member Posts: 542
    two words: route summarization
    = Marcus Drakonblayde
    ==[X]===[X]====[ ]=====[ ]====[ ]==
  • walid97walid97 Member Posts: 79 ■■□□□□□□□□
    This means that we use the "" network for both.. No need to type each subnet..
  • forbeslforbesl Member Posts: 454
    EIGRP summarizes by default. If you don't want it to summarize, you have to input "no auto-summary" into your EIGRP statement.

    router eigrp 2000
    no auto-summary

    This way the router will not summarize any networks in its EIGRP table, but will see all of the components of each network:

    one#show ip eigrp topology
    IP-EIGRP Topology Table for process 2000

    Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
    r - Reply status

    P, 1 successors, FD is 46354176
    via (46354176/45842176), Serial0
    P, 1 successors, FD is 11049472
    via (11049472/10537472), Serial0
    P, 1 successors, FD is 11023872
    via (11023872/10511872), Serial0
    P, 1 successors, FD is 2169856
    via Connected, Serial0

    Without turning off auto summarization, EIGRP would have summarized these networks to and
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