Cisco 1841 router DHCP problem

[Erik Boss]

Hi there,

we have a customer which has an 1841 router with IOS version c1841-ipbasek9-mz.124-24.T2.bin.

This customer has approx 300 clients.

I configured the following on the router:

interface FastEthernet0/0.6

encapsulation dot1Q 6

ip address 192.168.240.1 255.255.254.0

ip virtual-reassembly

ip tcp adjust-mss 1300

no cdp enable

ip dhcp pool ZELFSCAN

   network 192.168.240.0 255.255.254.0

   default-router 192.168.240.1

Pool ZELFSCAN :

Utilization mark (high/low)    : 100 / 0

Subnet size (first/next)       : 0 / 0

Total addresses                : 510

Leased addresses               : 239

Pending event                  : none

1 subnet is currently in the pool :

Current index        IP address range                    Leased addresses

192.168.241.234      192.168.240.1    - 192.168.241.254   239

As you see there a 239 clients with an IP-address, but like 50 clients without.

Does someone have an idea that the current IOS version has a bug in it?

I couldn't find anything in the release notes.

tnx

Regards,

Erik

[Erik Boss]

I made a workaround to add the DHCP scope on a local server and I disabled this one.

So we have to check the exact problem.

Regards,

Erik

[blau grana]

Hello Erik,

You should set reasonable lease time for DHCP. Now DHCP lease never expire and you can easily run out of free IPs.

Best Regards

Please rate all helpful posts and close solved questions

[Erik Boss]

Hi blau grana,

the lease is 8 days, that should be fine.

I have a lease for 510 IP-addresses, with 240 clients having an IP-address right now.

On smaller shops we don't have this similar issue and that works fine there.

With the DHCP-scope on the local server, still having the same problem.

Problem should exist in the wireless device, so we'll try to upgrade that one.

I saw the problem in the wireless controller.

Problem solved.

Regards

[paul driver]

Hello
Personally a good lease time for wired clients I would say be a max of 24 hrs with a renegotiation of half that lease time=12 hrs

Unless your clients are continuously login in a 8 day lease time can pose a security threat.

As for your wlan clients, a short lease time would be applicable especialy if clients are roaming and you are nearing dhcp starvation then a lease time of 2hrs would be a reasonable limit

res
Paul

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