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DHCP timeout on a vlan

jasonmeyer
Beginner
Beginner

Have a Cat9404 configure with several VLAN and each having Ip helper-address DHCP IP configured for each. Seems as though one VLAN DHCP requests for clients are timing out, though somewhat sporadically. I don't believe its a rogue DHCP server on the VLAN and as far as i know, only happening on one VLAN. 

 

Here is the DHCP section of a Show Tech DHCPV4

 

Message Received
BOOTREQUEST 1
DHCPDISCOVER 377041
DHCPREQUEST 970508
DHCPDECLINE 1783
DHCPRELEASE 680
DHCPINFORM 209273
DHCPVENDOR 0
BOOTREPLY 1
DHCPOFFER 361080
DHCPACK 1075473
DHCPNAK 236

Message Sent
BOOTREPLY 0
DHCPOFFER 0
DHCPACK 0
DHCPNAK 0

Message Forwarded
BOOTREQUEST 10
DHCPDISCOVER 3478790
DHCPREQUEST 9280023
DHCPDECLINE 17433
DHCPRELEASE 6361
DHCPINFORM 2025488
DHCPVENDOR 0
BOOTREPLY 1
DHCPOFFER 361080
DHCPACK 1075473
DHCPNAK 236

 

Shouldn't the received and forwarded be the same?

 

15 Replies 15

balaji.bandi
VIP Community Legend VIP Community Legend
VIP Community Legend

what vlan is that, what is the config on it ? how would you come that it was timing out, what is the observation here ?

 

BB

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Config is pretty straight forward.

 

interface Vlan2103
ip address x.x.x.x 255.255.0.0
ip helper-address DHCP IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip directed-broadcast 101
ip wccp 90 redirect in
ip wccp 92 redirect in

 

Well clients are self assigning addresses. On a windows client in the CLI I do an ipconfig /renew and it takes awhile but eventually returns a DHCP timeout error.

 

The apple netboot servers are for imagine Mac laptops and desktops, wish I didn't have to have so many. I have checked with the Apple admins and they say DHCP is not configured to hand out IPs, just boot info.

Hello,

 

what is the DHCP server (e.g. Windows 2012) ?

Window 2016.

Hello,

 

is there a specific reason for ip directed-broadasts to be enabled ? If not, try and disable that:

 

interface Vlan2103
ip address x.x.x.x 255.255.0.0
ip helper-address DHCP IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
ip helper-address apple netboot IP
--> no ip directed-broadcast 101
ip wccp 90 redirect in
ip wccp 92 redirect in

Thats in my other VLANs and not causing any issues there.

I did pull it out, just for fun.

As per i know i do not believe so many helper address works, i have tesed some time back, more than 4 helper address, the TTL expires, never reaches the DHCP Server., make it simple with ip helper address and test it.

BB

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Hmmm Ok I can see that, but other vlans have the exact same config and have been that way for several years and even different hardware and never had an issue.

i can not comment on how others working, just test as advice to see if that resolves your issue?

 

before we get to how others working with same config - we try to resolve the issue here.

 

BB

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Which 4 would you pull out? The last 4?

Try with only 1 DHCP which is reachable and working and keep adding more after testing.

 

BB

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friend, I think it issue of routing from DHCP server to host VLAN, you need to check the return traffic. try ping and see if it success.

If i statically assign an IP in the subnet, i can ping the DHCP server just fine. 

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