Campus Switching and Routing

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Occasional Contributor I

HPE 3810 switch, DHCP takes time

I've enabled DHCP server function on HPE 3810, but it takes almost 80 seconds to get an IP address from the switch. So I wonder, is this normal behavior? If not, I'd like to know how long time it is supposed to be.

Re: HPE 3810 switch, DHCP takes time

No, that is not normal. DHCP should be sub-second. Do you have only one DHCP server in that network? It can be that DHCP servers detect other/competing servers and back-off in that case to avoid conflicts.

 

Also, you can try to add the 'authoritative' keyword to your pool.

dhcp-server pool "vlan41"
   default-router "10.1.41.1"
   dns-server "10.254.1.254"
   lease 00:00:30
   network 10.1.41.0 255.255.255.0
   range 10.1.41.100 10.1.41.199
   authoritative
   exit

And check if you enabled the dhcp server, as by default it is disabled:

dhcp-server enable

If that doesn't help, I would do a packet capture from the client and monitor the DHCP process; and from the switch use the show dhcp-server commands to see if there is something that gives you a clue:

Aruba2930F# show dhcp-server
 binding               Show DHCP server IP address binding information.
 conflicts             Show DHCP server address conflict information.
 database              Show DHCP server lease database information.
 pool                  Show DHCP server address pool information.
 server-details        show dhcp-server database file transfer server details.
 statistics            Show DHCP server statistics information.
 <cr>
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Occasional Contributor I

Re: HPE 3810 switch, DHCP takes time

Herman, thank you for the advice.

I've tried as you mentioned, but unfortunately nothing has changed.

Instead, I found the following document which says DHCP delay is a bug and the new version will fix that.

 

============================================================

 

KB.16.03.0006 Release Notes

 https://support.hpe.com/hpsc/doc/public/display?docId=a00029001en_us

 

 P.30 Fixes "Version KB.16.03.0003"

 

  DHCP

 

  CR_0000222120

 

  Symptom: The switch DHCP server may delay honoring IP address renewal requests.

 

  Scenario: When a client which acquired an IP address from the switch DHCP server is

  roaming to a different VLAN also managed by the switch DHCP server, a fresh new DHCP

  client request process is initiated in place of the DHCP renewal request process,

  resulting in a longer delay for the DHCP client to acquire the new IP address.

  Workaround: Using an external DHCP server may help resolve the delay in DHCP client IP renewal

  when roaming from one VLAN to another.

 

============================================================

 

I haven't updated the switch yet, but I think this should solve the problem.

Re: HPE 3810 switch, DHCP takes time

This is correct. Let us know if the update fixed the delay. 

Re: HPE 3810 switch, DHCP takes time

is there any more detail as to what the fix was for this CR_0000222120 ? was it just to send a NAK rather than letting the dhcp timeout and release and then DORA again ? 

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