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Some part of the network is not receiving DHCP

xxcipherxx
Level 1
Level 1

Users from time to time is being disconnected to the network and will be online without any changes. 
One of the identified issue is the users cannot acquire IP address from and external dhcp server while others can. 

 

Please help. 

13 Replies 13

many many thing must check for this issue. 
first, are you using HSRP ?
are you use Catalyst 9000 series as Access-Agg-Core ??

No. We are using Catalyst 4500e as the core then mixed of 2900s and 3650/3850.

are you use HSRP ?

nope. we are not, sir.

if the Host not sending IP release to DHCP server, then DHCP server IP is exhausted.
two solution here 
increase the DHCP IP Pool 
decrease the Lease time. <<- do not make it soo short.  

balaji.bandi
Hall of Fame
Hall of Fame

check the DHCP scope is full, and you need to explain your setup ?

also check DHCP lease time ?

 

BB

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We are using a collapse core topology.

there are 4 switches that are directly connected to the core then the rest of the switches were under those 4. 

The issue is, when we are connecting to the 3/4 areas, we are not having any network disruptions/disconnectivity. only on a specific strand of the network and all through the end of the cascaded switches. 

 

dhcp is not full as checked with the administrators. 8 days for lease time. 

also, when we try to release/renew the ip config of the endpoint, it is not

8 days and DHCP not full. 

when you face issue, immediate access to SW that have VLAN of host and do, 
ping <DHCP server> source <SVI>

this give use indicate that the link is UP and DHCP is reachable between SW and DHCP server. 

the dhcp server is reachable from the gateway of the vlan.. 

only on a specific strand of the network and all through the end of the cascaded switches.

this where you need to start, CCC to chained switches need to look, Logs ? if this layer 2 STP ? if the Router make sure reachability to DHCP from VLAN Interface ?

also suggest to post working switch config and not working segment config will be helpfull ( at this stage no one knows what is the issue, until you post some evidence and information to analyse and suggest) if not we just playing in the dark.

BB

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what specific information do i need to post here, sir? 

there are two last thing 
first the buffer of 4500 <<- I make double check 
and second if the traffic is pass through FW. <<- can you use traceroute and see if the traffic hops is change 

also if you can 
debug dhcp detail <<- share this here

Hello
Can you share the dhcp pool statistics for the scopes, if not whats the utilization  ?


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Kind Regards
Paul
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