Ipconfig/release and renew problem ...

[sanjaynadarajah]

Hi,

I am having this problem for sometime and I need some help to solve this.

My problem is that I have a vlan whose clients are not getting an IP automatically (it is running DHCP). The user has to do an ipconfig/release and ipconfig/renew to get an IP.

The things that I have checked are the following :-

1) make sure that the ip helper-address is correct on the router interface.

Below is the interface configuration :-

interface Vlan90

description *** New Office Area ***

ip address 172.30.xxx.251 255.255.255.0

ip helper-address 198.175.110.100

ip helper-address 198.175.110.101

no ip redirects

no ip unreachables

no ip proxy-arp

ip pim sparse-dense-mode

ntp broadcast

end

2) I have set the speed/duplex to auto on the switch

end.

Can anyone give me a lead here so that I can further work on this problem ?

Thanking you in advance,

Cheers,

--Sanjay.

[aashish.c]

Hi Sanjay,

I`m sure you must have enabled portfast on host ports, but is mistakenly it is not then pls enable portfast on ports which are connected to workstations.

1. is DHCP server connected to same switch, whose config you have pasted here ?

2. which vlan DHCP server belongs to ?

3. Is DHCP server connected to same switch or behind the router. i mean

PC---------switch=--------router------DHCP ???

4. If server is connected directly to switch then enable portfast on that port as well.

Kindly update.

[johnyoon75]

plz, check the "ip forward-protocol"

[sanjaynadarajah]

Hi Aashish,

1) This is a remote site, the DHCP is at the central

site. The config is for the problematic vlan.

* I have another vlan that does the same function

on the same router and there is no such problem.

This is why I do not understand this. *

2) DHCP server belongs in a different vlan.

3) Yeah it is PC-Switch-Router-DHCP.

4) Yeah, I am double checking the switch port to make

sure that it has portfast enabled.

[5] Do you think that there is some command that is

missing on the DHCP that needs to be put in ???

-- Sanjay.

[aashish.c]

Hi Sanjay,

check these:

1. can u pls show me sh run of switch and router.

2. we also need to sniff the packets whether DHCP request unicast mesage is going from the switch to router or not.

sniffing will let us know whether request and response are traversing through switche and router or not.

3. just make sure than in "sh mac-address table" there is no address relearning or loop is not happening in problamatic vlan. bcoz i have seen omce that some MAC address was learned by some ports which were in membership of a vlan and they were not getting IP addreses automatically.

Kindly update after this...

Thanks

Aashish C

[sanjaynadarajah]

Hi Aashish,

Well it works fine now. The problem was those connection on vlan 90 was connnected to a Cat5500.

I moved those connections to the 4506 with SupIV.

The problem has been solved.

The connection was

4506(SupIV)

| (downlink)

|

Cat5500

[1] Therefore, could it be tht it is due to the fact that the 4506(SupIV) is using Native IOS and the Cat 5500 is using CatOS ?

[2] I noticed that the Cat500 is a bit slow through the telnet sesion. I checked this and the peak

utilization is 13% two days ago.

My assumption here it is due to [1] as if it can work on the Cat4056(SupIV) where the vlan resides, it should work fine on the Cat5500.

Thanks for your input Aashish. Really appreciate it.

--Sanjay.