CCNA's look inside please

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DustynF

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Here is the problem. I have ran out of Class C addresses and I don't have time to re-ipaddress all my devices on the network so I was wondering how i can route a class C an B network through a 1720 with only one ethernet port? Do I create a subinterface and put dual gateways for both classes of networks on the sub interfaces? There must be a way to do this other than change all the Ip's on my network to a class B right?
 
what type of hardware is connected to the Router's Ethernet port?

If you have it connected to a Cisco Switch, you could have multiple sub-interface's on the ethernet interface, and then put the new hosts into a different subnet... You would have to enable trunking on the switch(es) and router ethernet interface...

Personally, I am not familiar with 'secondary IPs', but you MIGHT be able to add a second IP address to the Ethernet interface...

Router>Enable
Router#Configure Terminal
Router(config)#interface ethernet0
Router(config-if)#ip address 192.168.1.2 255.255.255.0
Router(config-if)#ip address 10.1.1.2 255.255.255.0 secondary

again, I am not familiar with this command (just found it in a google search)... I did read (on CISCO's website) that you will have problems if you are using EIGRP for routing through that interface...

Can you give a more detailed description of the Topology of the network?
How many hosts are on this 'ethernet' segment, and how many are you adding.
Based upon your not wanting to change completly to class B, I have to assume that the network is using static addresses, not DHCP in the router.?

EDIT ok, that Cisco link isn't liking me... go to Cisco's homepage and search for 'secondary IP Address'
 
I have about 235 hosts right now and just recieved a grant that will give me about 150 more pc's. I am running all 3com unmanaged switches within my segment and yes I am also Running Eigrp and static routes to the other sites. Right now I am running 192.168.2.0 and want to route a 172.16.0.0 but the problem is that I can't route any traffic with my 192 default gateway. There must be some other way to route both classes to the head end.
 
Couple of questions:

Does the 172.16.x.x network already exsist?
If so, how many nodes?
What IOS version are you running on that 1720?
And how much Ram? I ask this only because subinterfacing comes to mind, as you stated above. This may be your best option, but, in my opinion, multiple c networks subinterfaced would be a more logical solution for you. Well, just makes more sense to me in my head and on paper.
 
IOS version 12.0
32k of nonvolile system memory
8192k of flash memory
Thanks guys for your help so far.

edit: yes the 172 network does exist

We have three other nodes one of them being the headend. Each site has a 1720 which then uses a t1 back to the headend which comes into a 2610 running nat with overload that jumps into a ISP router and off to the cloud.

All the other sites are running a class C network besides one site which has started to use the classB netowork. Can I do sunbinterfaces on my 1720?
 
I pretty busy atm so I don't have much time. I don't think that you are capable of subinterfacing because the IOS verion is too early. You need to have a version with IP+ coupled and enabled. I'm pretty sure that you version doesn't have it. Could be wrong there though. I'll need to do some searching later on.
 
Yes, after looking for a little while tonight, your IOS version doesn't have IP+ which you need to run subinterfacing.
 
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