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DHCP Lease Query

Vishal Kolamkar
Level 1
Level 1
Today i faced a strange issue regarding DHCP lease in our organisation. We have two DHCP server dedicated for wireless IP lease. One of the server scope was full & hence users IP should have been leased by secondary DHCP server, but secondary server was not leasing any IP hence new users were unable to connect. We have an ACL under the wifi SVI created under switch & users will be assigned with IP defined under that interface as below
Router#
!
int vlan 56
ip address 10.51.0.0 255.255.0.0
ip access-group vlan56-Untrusted in
!
Primary DHCP server 10.210.x.x whose scope was full as shown below opened with port bootps earlier by design. Till now whenever scope was full IPs were leased from secondary server 10.192.x.x without bootps ports.
Router#show access-lists vlan56-Untrusted | i 10.210.x.x
    170 permit udp any host 10.210.x.x eq bootps

After spending more than 5 hours i have added below bootps to try luck in order to allow for 10.192.x.x which resluted in immidiate 2 matches & users started connecting. IPs have been seen relaeased from this servers.
Router#show access-lists vlan56-Untrusted | i 10.192.x.x
  560 permit udp any host 10.192.x.x eq bootps (2 matches)

> Strange point is after 2 hits i am not seeing any hits increasing on ACL now neither there is any hits above dhcp acl line for 10.210.x.x.
> My doubt is now does bootps command is mandatory for DHCP to be functaional? Or its used as trigger for leasing IPs in some scenario?
> So far same setup was being used & was facing no issues as 10.192.x.x was only allowed to communcate over port domain. IPs were leased in past without bootps allowed.
Please share your thoughts
Regards,
Vishal



2 Replies 2

ahmedshoaib
Level 4
Level 4

Hi; 

You also configure the IP helper address for your 2nd DHCP Server or not?

Thanks & Best regards;

Yes its already configured.

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