A sample of a Frame Relay topology

i created a frame relay topology 10 minutes ago. Also, i managed to make it run. However, without no auto-summary command under end of the eigrp config on routers, routing didn't work. But it should have been because i had specified no autosummarization by entering wildcard for each advertised routes.

Why not without no auto summary?

I'll uploaded it for you to check it out. OK, here is the link ;

http://rapidshare.com/files/451547852/Frame_relay_ozg_networking.pkt

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Comments

alan2308

The problem is that you have discontinuous networks, which makes it unclear where to send certain packets when auto-summary is enabled. Both routers have routes to 10.0.0.0/8, so when a packet for either of those networks comes into a router, which way should it go? Router0 is going to want to send all packets for 10.0.0.0 to it's connected LAN, so anything for 10.6.1.0 will never be sent to Router1 so it'll never get to it's intended host on LAN 2.

Change the addressing on one of the LAN's to something outside of the 10.0.0.0/8 classfull network (such as 192.168.0.0/24) and everything will work as expected, even with auto-summary enabled.

networker050184

I'm not downloading anything, but the use of a wilcard mask does not remove auto summerization. The network statements only job is to tell the router what interface to run EIGRP on. It has no influence on what mask is advertised in routing updates.

thedrama

alan2308 wrote: »

The problem is that you have discontinuous networks, which makes it unclear where to send certain packets when auto-summary is enabled. Both routers have routes to 10.0.0.0/8, so when a packet for either of those networks comes into a router, which way should it go? Router0 is going to want to send all packets for 10.0.0.0 to it's connected LAN, so anything for 10.6.1.0 will never be sent to Router1 so it'll never get to it's intended host on LAN 2.

Change the addressing on one of the LAN's to something outside of the 10.0.0.0/8 classfull network (such as 192.168.0.0/24) and everything will work as expected, even with auto-summary enabled.

I know what discontiguous network is. Here, both networks (10.5.1.0 and 10.6.1.0) are subnetworks of a major network. Also, among them i configured a very different network. So there is a discontiguous structure.

However, i thought that when i typed network 10.5.1.0 0.0.0.255 with 10.6.1.0 0.0.0.255 means wildcards were able to save them off auto summary and as a result, they appear 10.5.1.0 and 10.6.1.0.

Well, how about if i used 10.7.1.0/24 among these two? Discontiguous
structure would be broken. Thats why, no auto summary shouldn't be
necessary that time ?

networker050184

I don't think you are quite understanding the network statement or auto summary.

Auto summary will summarize to the classfull boundary of 10.0.0.0/8. No matter what you use inside of that classfull network auto summary will break it.

thedrama

networker050184 wrote: »

I don't think you are quite understanding the network statement or auto summary.

Auto summary will summarize to the classfull boundary of 10.0.0.0/8. No matter what you use inside of that classfull network auto summary will break it.

Do you mean that typing wildcard on the network statement is useless and summarization occurs unless entering "no auto-summary" every time?

alan2308

thedrama wrote: »

Do you mean that typing wildcard on the network statement is useless and summarization occurs unless entering "no auto-summary" every time?

If auto summarization is enabled, then yes, the wild card is not very useful. But it depends on what routing protocol you're using whether or not auto-summary is enabled by default. In RIPv2 and EIGRP, it is enabled by default. In OSPF it is not.

This is why you'll often hear Jeremy Cioara say "when I see "auto" anything in Cisco, it reminds me that I "auto" not use it."

networker050184

thedrama wrote: »

Do you mean that typing wildcard on the network statement is useless and summarization occurs unless entering "no auto-summary" every time?

The network statement is ONLY used to identify the interface to run EIGRP on. It has nothing to do with summary or anything like that.

Chris_

thedrama wrote: »

Do you mean that typing wildcard on the network statement is useless and summarization occurs unless entering "no auto-summary" every time?

Yeah,I think you are confused about the network statement.

when you enter '10.5.1.0 0.0.0.255 ' this does not relate to 10.5.1.0 being a /24 subnet - it just means inculde anything where the mask is all 1s (the fourth octet in this case) as long as the first three are 10.5.1 (ie where the mask is all zeros) So this statement could include the network 10.5.1.0 /25 and 10.1.5.128 /25 or a whole bundle of /30 subnets.

it is just used to identify which interfaces/networks to include in the EIGRP process

But if you don't turn off auto summary all the other routers are going to see is 10.0.0.0/8 and from 2 directions!

thedrama

Thanks for the help.

Here comes another question about summarization. To make sure, i examined
that topic again. As i have searched, RIPv2 and EIGRP auto summarize by default. Moreover, EIGRP performs this at classful boundaries.

According to these, in order to avoid auto summary issue i tried slash notation other than /24 /16 and /8 such as by selecting /23 for each LAN. However, it didn't work without no auto-summary command. Is it caused by another Packet Tracer bug?

My networks are ;

(LAN) 172.16.30.0 /23 , (LAN) 172.16.40.0/23 10.3.1.0/24

Note: i am talking about different sample i set up before. (not the frame relay
topology)

alan2308

thedrama wrote: »

Thanks for the help.

Here comes another question about summarization. To make sure, i examined
that topic again. As i have searched, RIPv2 and EIGRP auto summarize by default. Moreover, EIGRP performs this at classful boundaries.

According to these, in order to avoid auto summary issue i tried slash notation other than /24 /16 and /8 such as by selecting /23 for each LAN. However, it didn't work without no auto-summary command. Is it caused by another Packet Tracer bug?

My networks are ;

(LAN) 172.16.30.0 /23 , (LAN) 172.16.40.0/23 10.3.1.0/24

Note: i am talking about different sample i set up before. (not the frame relay
topology)

Yes, RIPv2 and EIGRP auto-summarize based on classful boundaries by default, and OSPF will do the same if you manually enable it. That's how auto-summary works. It's called auto-summary because it summarizes your networks automatically. There's no bugs, it's supposed to do that.

In most cases, it's best to just disable auto-summary and not become frustrated by things that are actually working as they should.

Chris_

thedrama wrote: »

Thanks for the help.

Here comes another question about summarization. To make sure, i examined
that topic again. As i have searched, RIPv2 and EIGRP auto summarize by default. Moreover, EIGRP performs this at classful boundaries.

According to these, in order to avoid auto summary issue i tried slash notation other than /24 /16 and /8 such as by selecting /23 for each LAN. However, it didn't work without no auto-summary command. Is it caused by another Packet Tracer bug?

My networks are ;

(LAN) 172.16.30.0 /23 , (LAN) 172.16.40.0/23 10.3.1.0/24

Note: i am talking about different sample i set up before. (not the frame relay
topology)

I think you are still missing the point. Auto summarisation will always advertise networks with their default standard prefix length.

So in you rcase 172.16.30.0 will be advertised as 172.16.0.0/16 as it is 172.16.x.x IS a class B network!

10.3.1.0 will be advertised as 10.0.0.0/8 as 10.x.x.x is a class A network.

The only way to change this and advertise your VLSM subnets is to disable auto summary ..... ie 'no auto-summary' under the EIRGP process

Chris_

Also, if you're concerbned about packet tracer bugs, don't use it!! get GNS 3 and at least you know that if you come across a bug then it's an IOS bug.

thedrama

Chris_ wrote: »

I think you are still missing the point. Auto summarisation will always advertise networks with their default standard prefix length.

So in you rcase 172.16.30.0 will be advertised as 172.16.0.0/16 as it is 172.16.x.x IS a class B network!

10.3.1.0 will be advertised as 10.0.0.0/8 as 10.x.x.x is a class A network.

The only way to change this and advertise your VLSM subnets is to disable auto summary ..... ie 'no auto-summary' under the EIRGP process

I got it now. if i am not willing to be caught by autosummarization, i am supposed to suppress it by "no auto-summary" command every time.

Grateful to you for the situation.