I have a 9410R running Cisco IOS XE Software, Version 17.08.0. that seems to only intermittently process DHCP broadcasts across all VLANs, with users sometimes waiting up to 15 minutes to get an IP.
I have a PC connected directly to the switch, and this switch is the gateway. I've enabled DHCP debugging. Here's an example of one such time that it actually received my ipconfig /renew broadcast, sent it off, but never got the ack:
PLACEHOLDER#show logg | in f6c1|f6.c1
May 14 20:54:04.678: DHCPD: BOOTREQUEST from 018c.04ba.9ff6.c1 forwarded to 192.168.2.57.
May 14 20:54:04.678: DHCPD: BOOTREQUEST from 018c.04ba.9ff6.c1 forwarded to 192.168.2.67.
May 14 20:54:05.351: DHCPD: forwarding BOOTREPLY to client 8c04.ba9f.f6c1.
May 14 20:54:05.351: DHCPD: broadcasting BOOTREPLY to client 8c04.ba9f.f6c1.
But more often than not I see Wireshark send the broadcast and the switch log never logs the packet arriving, and the PC confirms that by never getting an IP in those moments.
I've even had it send to the DHCP server, get the ack and uni/broadcast it back, only for my PC to never receive it.
Then there are moments where I see the send, the helper processs, the ack, and I get an IP all in about 5 seconds - as it should be.
Both of which look exactly like this:
PLACEHOLDER#show logg | in f6c1|f6.c1
May 14 21:28:57.511: DHCPD: BOOTREQUEST from 018c.04ba.9ff6.c1 forwarded to 192.168.2.57.
May 14 21:28:57.511: DHCPD: BOOTREQUEST from 018c.04ba.9ff6.c1 forwarded to 192.168.2.67.
May 14 21:28:58.355: DHCPD: forwarding BOOTREPLY to client 8c04.ba9f.f6c1.
May 14 21:28:58.355: DHCPD: ARP entry exists (192.168.33.107, 8c04.ba9f.f6c1).
May 14 21:28:58.355: DHCPD: unicasting BOOTREPLY to client 8c04.ba9f.f6c1 (192.168.33.107).
I'm kinda at my wits end trying to resolve this.
interface Vlan33
ip address 192.168.33.121 255.255.255.0
ip helper-address 192.168.2.57
ip helper-address 192.168.2.67
no ip redirects
no ip proxy-arp
end
PLACEHOLDER#sh run int te7/0/13
Building configuration...
Current configuration : 93 bytes
!
interface TenGigabitEthernet7/0/13
switchport access vlan 33
switchport mode access
end
PLACEHOLDER#sh run | in dhcp
ip dhcp relay information trust-all
class-map match-any system-cpp-police-dhcp-snooping
ip dhcp relay information trusted
Most of the lines containing "dhcp" are in response to this problem. I added them because other posts suggested them. They haven't helped.
