Layer 2 UP Layer 3 Down on Ethernet WAN Links

Answered Question
Jun 15th, 2009


We have 2x separate ISP, one is use for Primary and the other is Backup. I'm using a Cisco 3825 with 3 Ethernet ports.

Configure using floating static with the backup set to 50 metric distance and route-maps for NAT between the two ISP networks.

ip route ISP1 name DEFAULT-ROUTE-ISP



route-map NAT-to-ISP2 permit 10

match ip address NAT_ACL

match interface GigabitEthernet0/1


route-map NAT-to-ISP1 permit 10

match ip address NAT_ACL

match interface GigabitEthernet0/0

The problem I recently experience is with Ethernet WAN service, ISP will provide a switch (usually a Cisco switch) to connect our WAN port too. From the ISP towards the WAN there is a fibre link going to the ISP network and if for some reason an outage occurs within the ISP network, the WAN link stays up due to CE to PE connection still active. Physical and protocol stays up on the CE route but next hop IP address is no longer reachable.

I actually found this solution:

Policy Based Routing with the Multiple Tracking Options

The only problem is I'm not running the correct IOS version ((C3825-ADVSECURITYK9-M), Version 12.4(7g)). Does anyone know of alternate solution similar to tracking?


I have this problem too.
0 votes
Correct Answer by Edison Ortiz about 7 years 4 months ago

Per the link you posted

"This feature was introduced in Cisco IOS® Software Release 12.3(4)T"

12.4 Mainline will definitely have PBR with Tracking options. The IP SLA commands may be a little different, follow the 12.4 Mainline doc:




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Overall Rating: 5 (1 ratings)
valdesp250503 Mon, 06/15/2009 - 17:54

Thanks Edison,

IP SLA with track works perfect for me.

Layer 3 down but physical and L2 is still up, the backup activates as the gateway last resort.



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