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mo shea
Beginner

Assign DHCP address for L3 routed ports on 6500

Hello,

Is there a way to assign DHCP address for L3 routed ports on 6500. I can do it on 4500 using IP address DHCP command, but for some reason the command is not supported on the 6500.

If the command is not supported, any idea how to go about it. The command is not supported on SVIs as well.

All help is appreciated.

19 REPLIES 19
Reza Sharifi
Hall of Fame Expert

Hi,

Under the SVI, "ip helper-address" command is not available?

HTH

Thanks Reza for the reply.

The command is there it relays the DHCP address to clients in the VLAN. So the  "ip helper-address" can be used to assign a DHCP address to an SVI ?

Reza Sharifi
Hall of Fame Expert

That is correct.  All you need is the "ip helper-address"

HTH

I am sorry. I completely misunderstood your question,

You are trying to assign an IP to a SVI using DHCP?

Not sure if you can do that under an SVI.

HTH

Thanks Jon and Reza for the reply, I believe your work on the forums have helped many people tremendously.

Back to my question, I am using 12.2(33)SXJ2 for the 6500. I prefer using L3 routed port rather than an SVI, but I need it to get its IP address dynamically

The scenario is for ships connecting to geographically dispersed sea ports. The ports are interconnected via WAN and the main DC is located in one of the ports. Now every ship has its own subnet and IP scheme, which is not known to us as we do not control the ship networks, but they need to communicate with our DC once they are connected to shore links.

Hence the ship L3 device connected to our 4500 L3 routed port supplies the latter with an IP address and this interface is routed  to our network. The surprising part was how come the 4500 supports this command and the 6500 doesn't. Even the 3850 supports it.

Jon Marshall
VIP Community Legend

Apologies for the delay in responding, I was going to reply and then thought of something else :)

I did a quick search and found a number of other people with the same issue and as far as I can tell it my well not be supported.

So when a ship comes into port do they physically connect from the switch at the port to the equipment on the ship and the switch at the port gets a DHCP IP address from the ship equipment so you can route to it.

Is that how it is meant to work ?

Jon

No worries Jon and thanks for the reply,

Your description is correct. The Ship switches physically connects to the port switches and supplies the latter with the IP address. It has been working perfectly on 4500 switches, thought of having a 6500 upgrade but such design wont be supported.

I wonder if there is another way to go about this issue in the 6500.

Regards

Jon Marshall
VIP Community Legend

I'm sure this is a stupid question but why can you not flip it round and have the ship's equipment get a DHCP IP from your 6500 ?

Would this mean you had to set things up on the ship equipment which you have no access to ?

Jon

It could be done either way, but if the sea port switch supplies the IP address then the admins of the WAN connected ports should create Vlans that do not overlap or else there would be conflicts as SVIs are always up. Also if 5 ships connect at once to a single port, 5 vlans on the port switch need to be unique.

It is just easier to let the ship supply the IP :) 

Reza Sharifi
Hall of Fame Expert

Hi,

You may want to talk to your Cisco SE and ask them about new features in the newer version of IOS coming out in the next 3 to 6 months.  I am not sure how much money your organization spends on Cisco products and support, but if the amount is significant, it can certainly have an effect in adding new features.

Since you are upgrading, the other thing that you may want to consider is that the 6500 series is being replaced with the 6800 series and although there are millions of 6500s out there, at some point Cisco will start retiring adding new features for this platform.

Are you using sup-2T?

Reza

We use sup VS-720. A friend of mine using Sup-2T on 6500 confirmed that the commands are not supported. I doubt the 6800 would be any different. Guess I have to downgrade to 3850.

Thanks for the feedback.

Regards

Moe Shea

Reza Sharifi
Hall of Fame Expert

I actually tried it on a 6800 that has later version of IOS and it is not available.

I tried it on our 95k switches and it is supported. I can move it there and somehow let the ASA (connected to 95k) obtain an IP address from the ships ... I still have to think it over

Regards,

Moe Shea

Jon Marshall
VIP Community Legend

Unless of course the ship equipment is a 6500 in which case just ignore what I said :)

Jon