urgent please help - 1721 config

[blackrabbit]

ok here is the setup, we currently have a cisco 1720 with one set of public ip addresses say 66.66.23.1 - 50 (these are fake numbers by the way) coming in off out t1 and going thourgh the built in 10/100 ethernet interface on the router. we also another block say 66.66.25.1 - 50 coming in of the t1 and going through the ethernet card plugged into slot0.

Our problem is we are setting up for using a 1721 with just the built in 10/100 ethernet interface and we want to know is it possible to get both sets of ip's to go through that one interface or do we need to change to say 66.66.23.1 - 100? Please help

 

[IllegalOperation]

Unless you have some sort of DSU/CSU, you need to terminate the T1 into a serial interface.

However, you can use subinterfaces on the ethernet side. It will provide you with two logical ethernet interfaces...

E0.1
E0.2

 

[blackrabbit]

i know, we have a t1 dsu/csu card in one slot and then an ethernet card in the other plus the built in ethernet. We want to do away with the extra ethernet card. right now each set of ip's goes to a separate card after it comes in off the dsu/csu card. we want to know if we can do both sets of ip's coming in off the dsu/csu can both go to one ethernet interface

 

[IllegalOperation]

If I understand this correctly, you have two different subnets coming off the same T1 circuit? I dont see why you wont be able to use one interface for that.

Like I said, all you need to do is assign each virtual interface a value - which is only locally significant. For example.... instead of normally using interface E0 - use interfaces E0.1 and E0.2. That creates two logical interfaces with their own potential configurations. So in your example, you can assign 66.66.23.0 to interface E0.1, and 66.66.25.0 can be assigned to interface E0.2.

 

[blackrabbit]

ok i'll try that and see if it works. thanks

 

[nyy1023]

another way of getting both blocks on the same interface is to set up
ip address x.x.x.x y.y.y.y secondary

This will allow you to configure two blocks on the same ethernet interface.

 

[blackrabbit]

cool i'll look into that, thanks.

 

[NetEng631]

Sorry but I have no Idea what you are talking about.

What do you mean by both sets of IP going through?

T1 Lines are point to point interfaces. Having 50 address on a T1 doesn't make sense. Are you saying you have a router advertizing the ethernet interface 66.66.23.0 network on the other side of the T1 or are they on the Ethernet interfaces?

Also are you running a routing protocol? If so what one. RIP OSPF BGP etc.

If your running a routing protocol or even static routes you should have no problem reaching each of these networks. If your trying to load babalnce thats a different story.

Please provide more info. Especially router configs with the IP addess and passwords blocked out.

 

[nyy1023]

if this works don't forget to click the helpful link!!!

 

[blackrabbit]

on out t-1 account we have 16 public ip's split into 2 ranges like x.x.x.x and x.x.y.x and the router sends the x.x.x.x to the FastEthernet0 interface and the x.x.y.x goes to the extra Ethernet card you can purchase for a cisco router. We basicaly want the x.x.x.x and the x.x.y.x to be piped through one interface on the router.

 

[nyy1023]

you can specify either one contigous block or add a secondary ip to the interface as specified above!!!

It will work...

I assume this last post was for Neteng631

 

[NetEng631]

Do you want to have two subnets x.x.x.x and x.x.y.x on the same Fast Ethrenet interface?

If this is the case then you can use
int f0/0
ip add x.x.x.x s.s.s.s
ip add x.x.y.x s.s.s.s secondary

http://www.cisco.com/en/US/products...eference_chapter09186a0080087387.html#1017863

or

Do you want to route both subnets out the same Serial interface using IP.
If this is the case, and you are not running a routing protocol, then you may need a static defualt route out the serial interface.

 

[blackrabbit]

yeah it was for Neteng631. I'm going to try that

 

[blackrabbit]

yeah we want both subnets going to the same FastEthernet Interface instead of slpittng them off onto seperate interface. I'm going to try the secondary thing. Thanks

 

[IllegalOperation]

The reason why I suggested subinterfaces instead of using a secondary IP, is because there could be routing issues. Depending on what your doing and how you are set up, some protocols will completely ignore the "secondary" subnet. For example, EIGRP updates always use the primary IP address of the outgoing interface as the source address.

I guess it is all a simple matter of how you are administratively set up, and personal preference....