Troubleshooting with DHCP

Hello Guys,

I need to have a solution for this problem:

2- Background: We have just installed this part of the network. Which consists of 2 routers connected to the same LAN. This LAN contains 30 servers and around 90 users. All servers do have a static ip address and the default gateway is R1 and all users do have an IP address learned by DHCP and their default gateway is R2.

3- Problem Description:

Around 1/3 users are experiencing internet connectivity problem.

The DHCP is configured correct and the same for default-router.

My solution in to add a last resort on R2 but I'm not sure.

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Comments

Trashman

Based on the information provided, all servers has working connectivity through R1.
R1 and R2 is in the same subnet and you are assigning IP addresses to users via DHCP.

Have you excluded the static assigned server IP addresses on your DHCP server?

OfWolfAndMan

1. How many users do you have?
2. What is your current subnet and mask?
3. As said above, have you excluded the statically assigned addresses from the pool?

pepsodent

there are 90 users, and the range for pool are 172.1.1.35 to 172.1.127 with subnet mask 255.255.255.128. They works everytime because it's a real-time troubleshooting. Yes, I think that static address are not incluse, but i'm not sure for this

Trashman

Please check and revert

Magic Johnson

Might this be a NAT issue?

pepsodent

I checked and the static address are excluded

pepsodent

there isn't NAT server

pepsodent

maybe Load balancing problem!

broli720

What about your switches? Have you started there? Could be a number of things: spanning tree incorrectly configured (is portfast enabled?), duplex issue (check interface speeds, might have to hard code them in). I would start from layer one and work my way up. Verify physical connectivity then move onto the layer two issues I mentioned. Let us know how it goes.

Magic Johnson

See when you say 'internet connectivity' does that mean access to the actual internet or internetwork connectivity as in can't ping anything?

Trashman

Can you please post more details in regards to configs on R1, R2 and R3.

You mention Internet connectivity problem.
Is it that 1/3 of users can't connect to Internet at all or is it that the Internet connection is unstable for those users?

Can you do a "ipconfig /all" on a user it is working for and the same for a user that it is not working for?

On a host that it is not working for, if you assign IP settings manually does it work?

pepsodent

this was a role play that cisco yesterday took me for valutation, and i only known what i wrote.
I don't have other information other configuration nothing!!

broli720

pepsodent wrote: »

this was a role play that cisco yesterday took me for valutation, and i only known what i wrote.
I don't have other information other configuration nothing!!

Well follow the troubleshooting steps that I listed for you. Research those topics if you're not familiar and you should be able to find possible solutions to your problem.

lantech

Unless the DHCP is configured improperly and is giving out the wrong information to 1/3 of the users then it's not a DHCP issue.

If the issue is an issue with the connection to the internet and not a problem where the users can't connect to the LAN at all then I think it would be more of a NAT issue than anything else. If the users can't connect to the LAN at all then there is a different issue. But the question does state that all the users have learned their settings from DHCP which would indicate that there is not an issue with the connection to the LAN itself.

cpartin

You said the static server addresses are excluded. Does that mean the server addresses are within the range of the pool and excluded, or that they're outside the range of the pool? Sorry to be pedantic, but your pool range is only 92 addresses and it seems awful fishy that you have 30 servers and problems with ~30 DHCP clients.

OfWolfAndMan

Alright so a few more questions:
1. Are all of these computers and servers running on different VLANs, and if so, have you configured your router or L3 switches for intervlan routing?
2. Assuming these users are connected to the same switch and not on the same vlan, can you ping each other?
3. Assuming your network is running on a domain, are all these computers connected to the domain?
4. Can the users login to the computer at least? If not, what is the error you get when trying to login?
5. Make sure your numbers are accurate. You may have to change your CIDR from /25 to /24 to increase the users from 126 users on the subnet to 254. We will need more info.