I'm back with yet another question

[mrconfused]

1.) When would you use the IGRP on a network?

2.) can you still + should you use a host table if you're using IGRP? I mean would it be pointless to do so? It seems like i'll be doing the work of IGRP if i decide to make a host table.

Thanks,
Mr Confused

 

[jgercken]

I would personally never implement IGRP. EIGRP has so many benifits over it.

Host tables map MAC to IP adddresses, replaces ARP broadcasts.

Routing protocols map IP addresses to next hops, replaces static routes.

They do completely different things.

----------------------------------------
Wassabi Pop Tarts! Write Kellogs today!

 

[mrconfused]

But you can use a host table on a router to set names for commonly used IP addresses. Which can help with troubleshooting or make life easier if your going to be testing a lot with pings. It would seem easier to type in the name than the complete address.

This is what i am wondering about. And to illustrate that I decide to use the IGRP protocol.(and while my example may somewhat insane...bare with me) If i am setting a host table (to make it easier when it comes to pinging) on the router then won't that be counter productive to have a protocol such as IGRP on the router active? Using an ex.

(All are IGRP 100)
Router 1 is connect two networks, E1 is 10.1.x.x and s0 is 12.x.x.x

Router 2 is directly connect 10.x.x.x from e1

router 3 is directly connected to 12.x.x.x from s0


Now from my understanding with IGRP configured i can ping
something on 10.x.x.x from router 3 without having any information about that router on router3.

But if i had a host table on router 3, router 2 and router 1 then part of the work that IGRP would've done. I've done by setting up a host table. Isn't this correct?

Thanks all
Mrconfused

 

[marsd]

You are talking about name resolution and routing and while one may depend on the other the reverse is not true.
Also all routers that know about routes propagated through igrp are running igrp, you ARE confused about that.

So if you use a dynamic routing protocol like igrp and
you have a route to 123.4.56.78, does it's hostname of
host.mydomain.com automagically resolve? No. But if you
map the address with a host statement then your router
remembers the name->address = host;, map and resolves.
However if for some reason, say a flapping interface,
igrp has lost an entry for that host network then no matter
what map exists the network is still unreachable.

Why not to use igrp?
It's a distance vector protocol at heart and cannot communicate subnet mask information, it is a "classful"
routing protocol, even though it is head and shoulders
above RIP V1 and even V2 in most every detail.
It is cisco proprietary.

If you have a small network with classful boundaries
then you can use RIP, for everything else why not use
something more flexible than igrp?

 

[ChrisAC]

Host tables and routing protocols are different things. I could set up an IP host called billybob with the IP address 212.50.x.y, but that doesn't mean that my router knows how to get to that IP address because it has a host entry. Routers route using routing protocols. IP hosts are just to make admin easier so you could ping or telnet or whatever to that host without having to look up the IP address. IGRP is used to advertise routes to other routers. Routes, not hostnames! The names don't matter as long as all your routers know how to reach other networks.

Don't confuse the two!

Chris.
**********************
Chris Andrew, CCNA, CCSA
chris@iproute.co.uk
**********************

 

[marsd]

Chris ,
What's the CCSA?
I'm CCNA/CCDA. Is it worth getting?

 

[ChrisAC]

Marsd,

It all depends on if you're into security. It's the CheckPoint Certified Security Administrator. I've also got the Security Expert exam in a few weeks. Then after Christmas I can work on the CCNP!

Chris.
**********************
Chris Andrew, CCNA, CCSA
chris@iproute.co.uk
**********************

 

[marsd]

Ah, I thought everything with CC**, had
a cisco cert behind it
No, I wouldn't work with Checkpoint or any
of the other commercial FW'(including PIX)
unless forced to..
Thanks.

 

[mrconfused]

From what i've read, this is what i've gather.

A host table without an IGRP (or any routing) protocol is worthless because there is no way for the router to know how to reach other networks.

Would it be worth the effort to have a host table on a router if i was using EGRP(or any other routing protocol) or should i stick to looking up the ip's when i need to ping? On the otherhand i can always stick a window's machine in the same room and ping from there. (entire network is window's based)

Thanks,
Mrconfused

 

[ChrisAC]

Oh jeez! One more time! IP Host names on routers and routing protocols are not related. From my router I can ping 216.45.19.33

Sending 5, 100-byte ICMP Echos to 216.45.19.33, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 168/170/176 ms
collossus#

Although I have no ip host entry for that address I can ping it because of ROUTING PROTOCOLS.

I could continue pinging 216.45.19.33 or I could create a host entry ..

collossus(config)#ip host tektips 216.45.19.33
collossus(config)#^Z
collossus#ping tektips

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 216.45.19.33, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 168/204/296 ms
collossus#

Personally I have a host table on my router just for helping troubleshooting. I can ping all our routers by name without having to remember all the IP addresses. However, if none of our routers had host tables they would still route correctly because routing protocols advertise IP routes, not hostnames.

Chris.
**********************
Chris Andrew, CCNA, CCSA
chris@iproute.co.uk
**********************

 

[mrconfused]

I guess i didn't make myself clear in the last post

What i meant to ask is if it's worth the tiem and effort to set up host tables for troubleshooting/pinging on mutltiple routers.


Mrconfused

 

[ChrisAC]

Okay, well yes if you plan to do extensive testing. It doesn't take that long to create host entries on the router as long as you don't do too many. I usually have about ten to fifteen tops of main routers on the network.

Chris.
**********************
Chris Andrew, CCNA, CCSA
chris@iproute.co.uk
**********************

 

[mrconfused]

great! thanks for the info

mrconfused