Client on FE interface can't ping 8.8.8.8 - Cisco 819 4G LTE

[Dennie]

Good afternoon everyone,

I have a Cisco C819G-4G-GA-K9 (LTE) router. The GigabitEthernet interface is my WAN interface.

I have connected a client to FE, but I cannot ping 8.8.8.8.
As soon as I disconnect GE, the Cellular0 interface jumps up and from then on the client on FE can ping 8.8.8.8.

Do you have any idea why I can't ping 8.8.8.8 with the client when the GE interface is connected?

I have attached the router configuration.

Thanks a lot in advance.

[Dennie]

I removed the backup interface command.

ip nat inside source list 2 interface Cellular0 overload
ip nat outside source list 1 interface Cellular0
ip route 0.0.0.0 0.0.0.0 GigabitEthernet0
ip route 0.0.0.0 0.0.0.0 Cellular0 10
!
access-list 1 permit 10.10.91.0 0.0.0.255
access-list 2 permit 10.10.91.0 0.0.0.255
access-list 23 permit 10.10.10.0 0.0.0.127

Thanks for your help!

[MHM Cisco World]

ip nat inside source route-map mhm1 interface g0 overload
ip nat inside  source route-map mhm2 interface Cellular0 overload 

Route-map mhm1 permit 10

Match ip address 1

Match interface g0

Route-map mhm2 permit 10

Match ip address 2

Match interface cellular0 

[Dennie]

I did that, but I still can't ping 8.8.8.8 with the client that is on fe0 when g0 is active.

[MHM Cisco World]

Share all config let me see

[Dennie]

Here you go

[MHM Cisco World]

All config is correct.

Can you use traceroute instead of ping and see where traffic stop?

[Dennie]

I have inserted a picture showing the tracert.

Zeitüberschreitung der Anforderung means Request timeout

[MHM Cisco World]

It can that ISP drop your request.

Ping Facebook public ip.

[Dennie]

Unfortunately it doesn't work either.

Does that perhaps help you?
I have created a VLAN in our main network so that I can simulate a WAN uplink on the LTE router.
As I understand it, the VLAN in the LTE router (interface vlan1) cannot ping 8.8.8.8. Do I need to assign a default gateway to the vlan (in this case 10.10.210.2)?

Or what else do you think could be the fault?

[Richard Burts]

I believe that there were 2 issues in your config. One of the issues was about NAT. You need address translation on both outgoing interfaces. Several posts suggest configuring the simple nat configuration on both outgoing interfaces. And you correctly report that this does not work. MHM has correctly suggested that when you want nat on 2 outgoing interfaces the solution is to use a route map in the nat configuration. The route map allows you to use a match statement for the acl and another match statement for the interface. Using this the na should be correct for both interfaces.

I think there may also be an issue about your default route "ip route 0.0.0.0 0.0.0.0 GigabitEthernet0". At best this is a weakness and perhaps is a severe problem. When you configure a static default route specifying only the outbound interface (not a next hop) and the outbound interface is Ethernet then it forces the router to arp for EVERY remote destination. This creates more load on the link to the upstream, it creates a very large arp table which consumes more memory and uses more cpu to maintain the arp table. That is the weakness part. The possible problem part is that many ISP will not respond to an arp request when the request is for an address that is not local. My suggestion is to change your default route to ip route 0.0.0.0 0.0.0.0 GigabitEthernet0 dhcp or perhaps to just  ip route 0.0.0.0 0.0.0.0 dhcp.

[MHM Cisco World]

can I see 
show ip nat translation when you ping or traceroute 

[Dennie]

Hello @MHM Cisco World and @Richard Burts,

thank you very much for your answers!

Attached is an image with the output of show ip nat translations, before I entered the command

ip route 0.0.0.0 0.0.0.0 dhcp

.

I have deleted the two routes and added the dhcp route. After that, my client on FE0 was still unable to ping 8.8.8.8. However, I then entered the command

ip route 0.0.0.0 0.0.0.0 cellular0

and then my client on FE0 was able to ping 8.8.8.8.

The client using the Cellular0 route to 8.8.8.8, although G0 is connected.

I have also attached the modified configuration.

[MHM Cisco World · Accepted solution]

the G0 have static IP 
then why you use static route with DHCP ?
you need to use 

ip route 0.0.0.0 0.0.0.0 g0 

[Dennie]

I have changed the G0 route again and entered my gateway behind it. Now I can ping 8.8.8.8 with my client that is connected to FE0.

These are the two routes that now work:

ip route 0.0.0.0 0.0.0.0 GigabitEthernet0 10.10.210.2
ip route 0.0.0.0 0.0.0.0 Cellular0 10

I would say that it was a complete success.

Thank you all for your help!

[MHM Cisco World]

You are so welcome 

Have a nice weekend 

MHM