LAN Interface Configuration Recommendation

[dacruzer1]

I need your recommendation.

I have a core router (ASR1001) and this router services 13 other remote router (ISR4321) via an ethernet link.

All 13 remote routers are coming in to Gi0/0/05 of the ASR1001.  Current configuration is this:

interface GigabitEthernet0/0/5

ip address 10.0.2.1 255.255.255.0
negotiation auto
cdp enable
end

The 13 routers are configured like this:

interface GigabitEthernet0/0/0

ip address 10.0.2.xx 255.255.255.0

My question is.. should I use VLSM and configure sub-interfaces for each of the 13 remote routers?

Any recommendations will be greatly appreciated.

[Reza Sharifi · Accepted solution]

So, you must have some sort of switch to collect all these 13 locations and than the switch connects to the ASR (0/0/5) right? You can put each location in a different subnet and configure 13 sub-interfaces for 13 locations.

location-1 10.10.1.2/24

location-2 10.10.2.2/24

location-3 10.10.3.2/24

and so on...

on the ASR

location-1 0/0/5.1 10.10.1.1/24

location-2 0/0/5.2  10.10.2.1/24

location-3 0/0/5.3 10.10.3.1/24

etc.. 

You can even use a smaller subnets (/28) if they are not serving LANs.

HTH

[dacruzer1]

Thanks Reza!

Can you tell me what would be the benefit of going to this configuration.

I appreciate your recommendation.

Thanks much!

[Reza Sharifi · Accepted solution]

So, one benefit would be if you make any changes to one subnet, it will not effect the other one or the other 12. The other benefit would be if say, you add a second router (ASR1000) for redundancy, you can create an HSRP group for each subnet and make the fail-over between the routers seamless. I think it is also makes it easier when you are dealing with provider failure and/or maintenance. 

HTH 

[dacruzer1]

Thanks Reza!  Especially for the quick response!

[Reza Sharifi]

Glad to help

Good luck!

Reza

[foua.yang@united.com]

Depends what you're trying to do but if its just a simple addressing I would just use a /28 because all you need is 14 host IPs. No subs needed.

ASR

interface GigabitEthernet0/0/5

ip address 10.0.2.1 255.255.255.240

-------------

ISRs

interface GigabitEthernet0/0/0

ip address 10.0.2."2-14" 255.255.255.240

This way you don't waste any IP space, if you need additional IPs for future growth just make it /27 or whatever depending on how many ISRs you plan to add.