02-16-2009 05:50 PM - edited 03-04-2019 03:35 AM
Hi,
We have an 1841 with 2 WAN Ints (Ethernet + SHDSL) - Both connected with /30 and running OSPF(Eth Interface has lower cost than SHDSL) and NAT. Failover works if eth is disconnected, but we have an additional /28 routed to the 1841....currently the /28 is statically routed to Ethernet Int, and also statically routed to SHDSL Int(But with a higher cost)....the /28 is used for PAT's to Internal Servers. When the Eth(WAN) Int is disconnected, the static route to the SHDSL Int does not take over....Therefore, to dynamically re-roure the /28 I think I would need to assign it to a Loopback Int, and have "redistribure connected subnets" enabled on ospf....How would I then use the /28 in PAT's?
02-17-2009 03:31 AM
Hello John,
actually having a loopback representing a NAT pool in a routing protocol for advertisement is a common practice.
You should be able to use your PAT statements.
I would suggest to use a network .. area command instead of a red conn in OSPF
add ip ospf network point-to-point to have OSPF advertise the correct mask under the loop interface
use for the loopback an ip address in the /28 that you are not using for the PATs this should be enough to have your PATs working.
Hope to help
Giuseppe
02-17-2009 05:22 PM
Thanks Giuseppe.
I have implemented what you suggested, but loop1's subnet is not being advertised by ospf - I have the following:
interface Loopback1
description LOOP_NAT
ip address 192.168.77.81 255.255.255.240
ip ospf network point-to-point
interface FastEthernet0/0
description WAN link$ETH-WAN$$FW_OUTSIDE$
ip address 192.168.75.130 255.255.255.252
ip verify unicast reverse-path
no ip redirects
no ip unreachables
ip nat outside
interface ATM0/3/0.96 point-to-point
description _FAILOVER
ip address 192.168.75.70 255.255.255.252
ip nat outside
router ospf 25
router-id 192.168.75.130
log-adjacency-changes
redistribute connected
redistribute static
passive-interface default
no passive-interface FastEthernet0/0
no passive-interface ATM0/3/0.96
no passive-interface Loopback1
network 192.168.75.68 0.0.0.3 area 25
network 192.168.75.128 0.0.0.3 area 25
network 192.168.77.80 0.0.0.15 area 25
Any help is greatly appreciated.
02-17-2009 06:10 PM
That looks right.
Perhaps you are filtering somewhere? Or try clear ip ospf proc (this will reset your ospf connections)
02-17-2009 06:37 PM
Hi,
No - no filtering.
I reset ospf process - Still no good.
Also tried removing ospf conf, and re-adding - Still no good.
This is what I currently have:
router ospf 25
router-id 192.168.75.130
log-adjacency-changes
passive-interface default
no passive-interface FastEthernet0/0
no passive-interface ATM0/3/0.96
no passive-interface Loopback1
network 192.168.75.68 0.0.0.3 area 25
network 192.168.75.128 0.0.0.3 area 25
network 192.168.77.80 0.0.0.15 area 25
#sh ip protocols
Routing Protocol is "ospf 25"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Router ID 192.168.75.130
Number of areas in this router is 1. 1 normal 0 stub 0 nssa
Maximum path: 4
Routing for Networks:
192.168.75.68 0.0.0.3 area 25
192.168.75.128 0.0.0.3 area 25
192.168.77.80 0.0.0.15 area 25
#sh ip ospf database self-originate
OSPF Router with ID (192.168.75.130) (Process ID 25)
Router Link States (Area 25)
Link ID ADV Router Age Seq# Checksum Link count
192.168.75.130 192.168.75.130 323 0x80000003 0x00B1DE 4
02-17-2009 11:59 PM
Hello John,
I don't see anything wrong here.
First of all, from sh ip protocols you see the router declares
Routing for Networks:
192.168.77.80 0.0.0.15 area 25
Then when you look at the OSPF database be aware that the router LSA is a single data structure with a label = OSPF router-id but that inside has information for multiple links
see
Link ID ADV Router Age Seq# Checksum Link count
192.168.75.130 192.168.75.130 323 0x80000003 0x00B1DE 4
link count is 4 (point-to-point links count for two):
two for the ATM
one for lan
one for loopback
you need to check if the prefix 192.168.77.80/28 is seen on other routers
or also you need to look at the details of this router LSA
Everything looks like fine and removing the redistribute connected can have helped.
Hope to help
Giuseppe
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