ISR4321 Not Requesting or Just Not Getting DHCP Address From ISP Modem?

[Matthew Martin]

Hello All,

Device: ISR4321

Last Friday I upgraded the IOS-XE image on this ISR device from 03.13.04.S to 03.16.05.S... Ever since this upgrade, interface Gi0/0/0 no longer receives a DHCP Address from the ISP's modem, which is connected directly to Gi0/0/0. Prior to the upgrade this was working just fine.

Now, we first attempted to reboot the Modem (*actually tried this a few times), but that didn't seem to help. So next, we unplugged the Ethernet cable going from the ISP's Modem --to--> the ISR, so that it was now going from the ISP Modem, directly into a Laptop. After a few seconds the laptop received an IP address via DHCP and I was able to get on the internet without issue.

After that test we reconnected the Ethernet cable back into port Gi0/0/0 and it still will not get an IP Address.

I enabled "debug ip dhcp server events", but the ONLY debug data referring to Gi0/0/0 are the lines shown below, which print out 3 consecutive times, just like this, every couple of minutes:

Apr 13 17:10:49.455: DHCPD: IP address change on interface GigabitEthernet0/0/0
Apr 13 17:10:49.455: DHCPD: IP address change on interface GigabitEthernet0/0/0
Apr 13 17:10:49.457: DHCPD: IP address change on interface GigabitEthernet0/0/0

But, that's it. That's the only info referring to this interface printed to the log.

show ip int brief:

ISR-4321# show ip int brief
Interface              IP-Address      OK? Method Status                Protocol
GigabitEthernet0/0/0   unassigned      YES DHCP   up                    up      
GigabitEthernet0/0/1   unassigned      YES NVRAM  up                    up      
GigabitEthernet0/0/1.1 10.3.1.1        YES NVRAM  up                    up      
GigabitEthernet0/0/1.2 10.3.2.1        YES NVRAM  up                    up      
GigabitEthernet0/0/1.7 10.3.7.1        YES NVRAM  up                    up      
Serial0/1/0:0          ww.xxx.yy.zz    YES NVRAM  up                    up      
Service-Engine0/2/0    unassigned      YES unset  up                    up      
Service-Engine0/4/0    unassigned      YES unset  up                    up      
GigabitEthernet0       unassigned      YES NVRAM  administratively down down

show run interface Gi0/0/0:

JWP-4321-BIS#show run int Gi0/0/0
Building configuration...

Current configuration : 236 bytes
!
interface GigabitEthernet0/0/0
 description ISP Gateway
 ip dhcp client client-id GigabitEthernet0/0/0
 ip address dhcp
 ip nat outside
 zone-member security INTERNET
 media-type rj45
 negotiation auto
end

Since this was working just fine prior to upgrading the ISR device, I have to assume it has something to do with that... Also, we have about 8 branch office locations, each with their own local Broadband internet connection which is setup in the same way as this location (*same ISR4321 model in each). The only difference is that the ISP in this location does not give us access to the Modem's configuration so we had to go with DHCP. And that's the only difference between this location and all the rest. And also, all of the other locations have all been upgraded to this same IOS-XE version mentioned above, but none of them are having trouble (*but this is only location needing dhcp on the Gi0/0/0 interface)...

I'm kind of stumped on what I can do now to get this working other then possibly downgrading back to the old version, however the old version did not have the "ip dns server" command, which is why we needed to upgrade, so we chose the current CIsco recommended version for ISR4321s...

Any thoughts or suggestions would be greatly appreciated!

Thanks in Advance,
Matt

[Reza Sharifi]

Hi,

What happens when you connect the modem to g0/0/1 instaed?

If it acts the same way, you may want to open a ticket with TAC and have them look. 

HTH

[Matthew Martin]

Hey Reza, thanks for the reply.

I would attempt to try it in Gi0/0/1, but that port is configured for the LAN, which goes to a 2960X switch, and Gi0/0/1 has about 3 or 4 subinterfaces configured on it so I'd rather not try to remove that configuration to add dhcp.

I just opened a TAC case on Friday, so I guess we'll see what they say.

On the configuration for 0/0/0, are the "ip dhcp client  <client-id/class-id/hostname/etc...>" commands necessary for dhcp to work, or is it the case that when you add those commands, like "ip dhcp client client-id", are they just overwriting what would be the default values for those?



Thanks Again,
Matt

[Matthew Martin]

It's working now..!

Removing the "ip nat outside" command from Gi0/0/0 suddenly got the interface working again and it can now get a DHCP address from the attached ISP modem...

So for some reason after upgrading from 03.13.04.S to 03.16.05.S, having the "ip nat outside" command prevented Gi0/0/0 from getting a DHCP Address. Any ideas why that would cause a problem in the new version and not the older one?

Thanks,
Matt

[scott.bridges]

I know this is years old, but Google brought me here and put me down the right path to fix, so I thought I'd share:

I had a very similar problem:  ASR1k, Gi1/0/0 connected to ISP that is handing out DHCP, but no IP would come up.

Long story short, it appeared to be a NAT/ACL bug.  I had "ip nat outside" and ACL was "acl 1 permit 0.0.0.0" for a catch-all.  I changed this ACL to the specific /24 subnets I needed to NAT -- and got rid of the 0.0.0.0.  I was then able receive DHCP on Gi1/0/0

Hope this helps.

[switched56]

I can confirm this resolved the same issue I was seeing on my ISR 4461, running isr4400v2-universalk9.17.16.01a.SPA.bin.

To this point I had been defaulting the interface config (including removing ip nat outside) and reapplying it via a daily kron job.

[B Taylor]

Unbelievable....  SEVEN years later and this issue STILL exists!!

So grateful to have found this thread as I too was pulling my hair out on not getting a DHCP address.  I had ip nat outside and the permit any list on the Nat statement.  As soon as I removed ip nat outside, the interface immediately got an address.  I changed the permit any nat ACL to have specific ranges (internal vlan and VPN pool) and its working with the ip nat outside back on the interface.

Here's the kicker - I'm running an ISR 4k with 17.12 code!  So the bug/issue prevails.....

Thank you.