10-23-2025 06:07 PM
Dear Forum,
I'm reaching out for an issue I'm having with a Cisco 1100 running IOS 9.17.09.05. The router is connected to 2 WAN ports with a simple failover config. The primary WAN is on G0/0/0 and the backup is on G0/0/1. When ISP1 (ATT) drops, the default route is changing to ISP 2 (Comcast) but it will not route past the gateway. Nat tables don't show any entries on the tables when it cuts over.
Troubleshooting steps I've tried:
1. Verified static IP information and route on the ISP 2.
2. Tried forcing a network out directly to ISP 2 with policy mapping on a single VLAN.
3. Tried adding track 10 and track 10 with SLA's on both interfaces.
4. Tried standard ACL's to see if there is anything blocking the outbound.
I have a single site to site VPN that's not applied right now but it's only on the primary interface. For the config I have:
boot system bootflash:c1100-universalk9.17.09.05a.SPA.bin
ip name-server 1.1.1.1 8.8.8.8 10.17.1.200
!
track 10 ip sla 10 reachability
!
!
!
!
!
!
!
!
!
crypto isakmp policy 1
encryption 3des
hash md5
authentication pre-share
group 2
crypto isakmp key XXXXXXX address XXX.XXX.XXX
crypto isakmp keepalive 60 30
!
!
crypto ipsec transform-set SRAWH esp-3des esp-md5-hmac
mode tunnel
!
crypto ipsec profile XXX
set transform-set XXX
!
!
!
crypto map XXX 10 ipsec-isakmp
set peer X.X.X.X
set transform-set XXX
match address XXXX
!
!
!
!
!
!
!
!
interface Tunnel0
ip address 10.19.1.250 255.255.255.240
tunnel source X.X.X.X
tunnel destination X.X.X.X
tunnel protection ipsec profile XXXX
!
interface GigabitEthernet0/0/0
description ATT
ip address X.X.X.X 255.255.255.248
ip nat outside
negotiation auto
!
interface GigabitEthernet0/0/1
description COMCAST
ip address X.X.X.X 255.255.255.248
ip nat outside
negotiation auto
!
interface GigabitEthernet0/1/0
description Link to LAN
switchport mode trunk
!
interface GigabitEthernet0/1/1
description Link to PBX
switchport access vlan 30
switchport mode access
!
interface GigabitEthernet0/1/2
switchport access vlan 10
switchport mode access
!
interface GigabitEthernet0/1/3
description Monitoring System
switchport mode access
!
interface Vlan1
ip address 10.1.1.250 255.255.255.0
ip nat inside
!
interface Vlan10
ip address 10.17.1.206 255.255.255.240
ip nat inside
!
interface Vlan11
description MGMT
ip address 10.17.1.14 255.255.255.240
ip helper-address 10.17.1.200
ip nat inside
!
interface Vlan12
description REGULATORY
ip address 10.17.1.30 255.255.255.240
ip helper-address 10.17.1.200
ip nat inside
!
interface Vlan14
description BUSDEV
ip address 10.17.1.46 255.255.255.240
ip nat inside
!
interface Vlan15
description ACCOUNTING
ip address 10.17.1.62 255.255.255.240
ip helper-address 10.17.1.200
ip nat inside
!
interface Vlan20
description CLINOPS
ip address 10.17.2.250 255.255.255.0
ip helper-address 10.17.1.200
ip nat inside
!
interface Vlan30
description VOICE
ip address 10.17.3.250 255.255.255.0
ip nat inside
!
interface Vlan40
description CAMERAS
ip address 10.17.4.250 255.255.255.0
ip nat inside
!
interface Vlan50
description GUEST
ip address 10.17.5.250 255.255.255.0
ip nat inside
!
interface Vlan60
description ACCESSCNTRL
ip address 10.17.6.250 255.255.255.0
ip nat inside
!
interface Vlan70
description DATALOGGER
ip address 10.17.7.250 255.255.255.0
ip nat inside
!
ip local policy route-map IPSLA10
no ip http server
ip http authentication local
no ip http secure-server
ip forward-protocol nd
ip nat settings interface-overload block port tcp 5150
ip nat settings interface-overload block port tcp 5160
ip nat inside source static tcp 10.17.4.200 5150 X.X.X.X 5150 extendable
ip nat inside source static tcp 10.17.4.200 5160 X.X.X.X 5160 extendable
ip nat inside source list 101 interface GigabitEthernet0/0/0 overload
ip nat inside source list 102 interface GigabitEthernet0/0/1 overload
ip route 0.0.0.0 0.0.0.0 X.X.X.X track 10 (ATT)
ip route 0.0.0.0 0.0.0.0 X.X.X.X 2 (Comcast)
ip route 10.12.1.0 255.255.255.0 Tunnel0
ip route 10.12.2.0 255.255.255.0 Tunnel0
ip route 10.12.3.0 255.255.255.0 Tunnel0
!
!
ip access-list extended IPSLA10
10 permit icmp X.X.X.X (ATT) 0.0.0.7 8.8.8.8 0.0.0.3
ip access-list extended SRAWHVPN
10 permit ip 10.17.1.0 0.0.0.255 10.12.1.0 0.0.0.255
20 permit ip 10.17.2.0 0.0.0.255 10.12.2.0 0.0.0.255
30 permit ip 10.17.3.0 0.0.0.255 10.12.3.0 0.0.0.255
!
ip sla 10
icmp-echo 8.8.8.8 source-interface GigabitEthernet0/0/0
timeout 6000
frequency 10
ip sla schedule 10 life forever start-time now
ip access-list extended 101
10 deny ip 10.1.1.0 0.0.0.255 10.12.1.0 0.0.0.255
20 deny ip 10.17.1.0 0.0.0.255 10.12.1.0 0.0.0.255
30 deny ip 10.17.2.0 0.0.0.255 10.12.2.0 0.0.0.255
40 deny ip 10.17.3.0 0.0.0.255 10.12.3.0 0.0.0.255
50 deny ip 10.17.4.0 0.0.0.255 10.12.4.0 0.0.0.255
60 deny ip 10.17.5.0 0.0.0.255 10.12.5.0 0.0.0.255
70 deny ip 10.17.6.0 0.0.0.255 10.12.2.0 0.0.0.255
80 deny ip 10.17.7.0 0.0.0.255 10.12.2.0 0.0.0.255
90 permit ip 10.1.1.0 0.0.0.255 any
100 permit ip 10.17.1.0 0.0.0.255 any
110 permit ip 10.17.2.0 0.0.0.255 any
120 permit ip 10.17.3.0 0.0.0.255 any
130 permit ip 10.17.4.0 0.0.0.255 any
140 permit ip 10.17.5.0 0.0.0.255 any
150 permit ip 10.17.6.0 0.0.0.255 any
160 permit ip 10.17.7.0 0.0.0.255 any
ip access-list extended 102
1 deny ip 10.1.1.0 0.0.0.255 10.12.1.0 0.0.0.255
2 deny ip 10.17.1.0 0.0.0.255 10.12.1.0 0.0.0.255
3 deny ip 10.17.2.0 0.0.0.255 10.12.2.0 0.0.0.255
4 deny ip 10.17.3.0 0.0.0.255 10.12.3.0 0.0.0.255
5 deny ip 10.17.4.0 0.0.0.255 10.12.4.0 0.0.0.255
10 deny ip 10.17.5.0 0.0.0.255 10.12.5.0 0.0.0.255
20 deny ip 10.17.6.0 0.0.0.255 10.12.6.0 0.0.0.255
30 deny ip 10.17.7.0 0.0.0.255 10.12.7.0 0.0.0.255
40 permit ip 10.1.1.0 0.0.0.255 any
50 permit ip 10.17.1.0 0.0.0.255 any
60 permit ip 10.17.2.0 0.0.0.255 any
70 permit ip 10.17.3.0 0.0.0.255 any
80 permit ip 10.17.4.0 0.0.0.255 any
90 permit ip 10.17.5.0 0.0.0.255 any
100 permit ip 10.17.6.0 0.0.0.255 any
110 permit ip 10.17.7.0 0.0.0.255 any
!
route-map IPSLA10 permit 10
match ip address IPSLA10
set ip next-hop X.X.X.X (ATT GW)
sho ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, m - OMP
n - NAT, Ni - NAT inside, No - NAT outside, Nd - NAT DIA
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
H - NHRP, G - NHRP registered, g - NHRP registration summary
o - ODR, P - periodic downloaded static route, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR
& - replicated local route overrides by connected
Gateway of last resort is X.X.X.X (ATT) to network 0.0.0.0
S* 0.0.0.0/0 [1/0] via X.X.X.X (ATT)
10.0.0.0/8 is variably subnetted, 24 subnets, 3 masks
C 10.1.1.0/24 is directly connected, Vlan1
L 10.1.1.250/32 is directly connected, Vlan1
C 10.17.1.0/28 is directly connected, Vlan11
L 10.17.1.14/32 is directly connected, Vlan11
C 10.17.1.16/28 is directly connected, Vlan12
L 10.17.1.30/32 is directly connected, Vlan12
C 10.17.1.32/28 is directly connected, Vlan14
L 10.17.1.46/32 is directly connected, Vlan14
C 10.17.1.48/28 is directly connected, Vlan15
L 10.17.1.62/32 is directly connected, Vlan15
C 10.17.1.192/28 is directly connected, Vlan10
L 10.17.1.206/32 is directly connected, Vlan10
C 10.17.2.0/24 is directly connected, Vlan20
L 10.17.2.250/32 is directly connected, Vlan20
C 10.17.3.0/24 is directly connected, Vlan30
L 10.17.3.250/32 is directly connected, Vlan30
C 10.17.4.0/24 is directly connected, Vlan40
L 10.17.4.250/32 is directly connected, Vlan40
C 10.17.5.0/24 is directly connected, Vlan50
L 10.17.5.250/32 is directly connected, Vlan50
C 10.17.6.0/24 is directly connected, Vlan60
L 10.17.6.250/32 is directly connected, Vlan60
C 10.17.7.0/24 is directly connected, Vlan70
L 10.17.7.250/32 is directly connected, Vlan70
50.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C X.X.X.X (Comcast)/29 is directly connected, GigabitEthernet0/0/1
L X.X.X.X (Comcast)/32 is directly connected, GigabitEthernet0/0/1
107.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C X.X.X.X (ATT)/29 is directly connected, GigabitEthernet0/0/0
L X.X.X.X (ATT)/32 is directly connected, GigabitEthernet0/0/0
Any suggestions would be greatly appreciated. I've been battling with this for a week now. I've even tried the solution in another thread:
https://community.cisco.com/t5/routing/cisco-1100-router-dual-wan-configuration/td-p/4754796
But it doesn't seem to properly fail over.
Thank you everyone for an suggestions
Solved! Go to Solution.
10-24-2025 12:10 AM
Hello @InSysProllc ,
when dealing with NAT over multiple WAN L3 uplinks the NAT configuration needs to use route-maps in NAT statement like
route-map ISP_1 permit 10
match ip address 101
match interface GigabitEthernet0/0/0
!
route-map ISP_2 permit 10
match ip address 101
match interface GigabitEthernet0/0/1
please notice that the match interface in this case matches the outgoing interface and this is the key to make NAT to work.
In this way when you are using the first WAN interface only the first route-map matches. If using the second WAN the second route-map matches making NAT to work without ambiguity.
ip nat inside source route-map ISP_1 interface GigabitEthernet0/0/0 overload
ip nat inside source route-map ISP_2 interface GigabitEthernet0/0/1 overload
I have taken this example from the thread you have linked
You should change your NAT config to use something like the above example.
Hope to help
Giuseppe
10-24-2025 12:10 AM
Hello @InSysProllc ,
when dealing with NAT over multiple WAN L3 uplinks the NAT configuration needs to use route-maps in NAT statement like
route-map ISP_1 permit 10
match ip address 101
match interface GigabitEthernet0/0/0
!
route-map ISP_2 permit 10
match ip address 101
match interface GigabitEthernet0/0/1
please notice that the match interface in this case matches the outgoing interface and this is the key to make NAT to work.
In this way when you are using the first WAN interface only the first route-map matches. If using the second WAN the second route-map matches making NAT to work without ambiguity.
ip nat inside source route-map ISP_1 interface GigabitEthernet0/0/0 overload
ip nat inside source route-map ISP_2 interface GigabitEthernet0/0/1 overload
I have taken this example from the thread you have linked
You should change your NAT config to use something like the above example.
Hope to help
Giuseppe
10-24-2025 11:57 AM
Hello Giuseppe,
Thank you very much for suggestion. I have some downtime on the site tomorrow so I can test and provide feedback.
Thanks!!
10-25-2025 12:17 PM
That solution worked! Thank you for the suggestion!
I've posted the updated brief config for anyone who may encounter the same issue:
track 10 ip sla 10 reachability
!
ip local policy route-map IPSLA10
!
ip nat inside source route-map ISP_1 interface GigabitEthernet0/0/0 overload
!
ip nat inside source list route-map ISP_2 interface GigabitEthernet0/0/1 overload
!
ip route 0.0.0.0 0.0.0.0 X.X.X.X track 10 (ISP_1)
ip route 0.0.0.0 0.0.0.0 X.X.X.X 2 (ISP_2)
!
ip access-list extended IPSLA10
10 permit icmp X.X.X.X (ISP_1) 0.0.0.7 8.8.8.8 0.0.0.3
!
ip sla 10
icmp-echo 8.8.8.8 source-interface GigabitEthernet0/0/0
timeout 6000
frequency 10
ip sla schedule 10 life forever start-time now
!
ip access-list extended 101 (Example)
!
route-map ISP_1 permit 10
match ip address 101
match interface GigabitEthernet0/0/0
!
route-map ISP_2 permit 10
match ip address 101
match interface GigabitEthernet0/0/1
!
route-map IPSLA10 permit 10
match ip address IPSLA10
set ip next-hop X.X.X.X (Primary GW)
The only other note was adding an ACL to send the icmp through the primary gateway only to prevent mismatches on the ISP side.
Thank you Giuseppe for the assistance!
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