Question about OSPF failover

[Andrew Cormier]

Good day!

I have a switch in my server room

I also have a switch at a secondary server room at a site 5 miles away

I have two separate LANEXs (1Gb each) connecting the switches. This is for fault tolerance if someone pulls down the fibre (as happened a couple of years ago).

I am using OSPF to route between the two switches. It seems to be balancing the traffic between the two links (not a bad thing)

My default gateway for the switch in my server room is both the endpoints at the other location (since that is where our internet connection is)

ip route 0.0.0.0 0.0.0.0 172.18.10.2 5

ip route 0.0.0.0 0.0.0.0 172.18.11.2 5

(10.1 and 11.1 are here ..)

When I unplug one of the links to test, I lose connectivity to the other site. I only left it unplugged maybe 5-10 seconds (an OH S#it! moment ) since I thought the failover to the second route.

Shouldnt OSPF detect the other route to be unavailable fairly quickly and increase the cost? or is it the fact that I am specifying the cost that screws up the failover? Or am I just a newb and impatient?

[Andrew Cormier]

SUCCESS! (well as far as I am concerned). I unplugged one of the links ... didnt lose connectivity to the other site.

Went and got a coffee. Came back and was still good. Plugged the link back in and waited 5 min. Unplugged the other link and lost connectivity... for about 30 seconds or so ... then it came back. Good enough for me!

Thanks for all the help

Drew

[dsolangon]

It will prioritised the static route try to increase the cost of your static route then it will serve as a backup routing if you can post you diagram you can use hsrp or something bla bla depends on the net work design

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[Andrew Cormier]

Well it worked for about 4 hours and then died. I had to kill one of the links and remove its route.

When it died connectivity between the sites was ok but internet browsing was very slow (we route our internet traffic out through the other site) This is why I had the

ip route 0.0.0.0 0.0.0.0 172.18.X.2  lines

[chris.monk]

Andrew,

If you are redistributing the static default route from your remote office into ospf, you do not really need those static default routes on your side.

Also, I meant to ask.  Why are you using VLANs as point to point links?  Is there a certain need for this?  Just curious...

[Andrew Cormier]

Someone else had set up the VLANS before.

We used to have a 1Gb link and a 100mb link. The 100mb was strictly for emergencies. We stopped using it years ago but kept the vlans.

Sorry to be dense but if I dont have those dgw routes specified how do I get all my outbound traffic to route out through the other site?

[chris.monk]

Post the output of "show IP ospf database" that will tell us if you are getting a default route from your remote site.

Sent from Cisco Technical Support Android App

[Andrew Cormier]

Hi Chris, The plot thickens here.

So, yesterday morning (6am) I unplugged one of our two links. Slight blip but connectivity remained between the two sites. I reconnected... waited a little and unplugged the second link. Blib but again, nothing major. I figured that was enough and patted myself on the back and thanked you. I did not check web browsing (I should have)

Yesterday morning (10am) our ISP had a problem and one of the two links went down. Connectivity between the sites stayed up but internet browsing ground to a halt. The ISP confirmed a link went down but doesnt think our internet access would have been affected (browsing from the other site was fine so I tend to believe him.)

Here is the other info you asked for

router ospf 1 *remote site*
log-adjacency-changes
auto-cost reference-bandwidth 10000
redistribute static metric 1000 subnets
network 10.0.0.0 0.255.255.255 area 0
network 172.18.1.2 0.0.0.0 area 0
network 172.18.2.2 0.0.0.0 area 0

router ospf 1 *local site*
log-adjacency-changes
auto-cost reference-bandwidth 10000
redistribute static metric 1000 subnets
network 10.30.0.0 0.0.255.255 area 0
network 10.0.0.0 0.255.255.255 area 0
network 172.16.0.0 0.0.255.255 area 0
network 172.17.0.0 0.0.255.255 area 0
network 172.18.1.1 0.0.0.0 area 0
network 172.18.2.1 0.0.0.0 area 0

__________________________________________________
*remote site *
#sho ip ospf datab

            OSPF Router with ID (172.18.2.2) (Process ID 1)

                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
172.18.2.1      172.18.2.1      1877        0x8000094C 0x006CDD 27
172.18.2.2      172.18.2.2      170         0x80007A4A 0x00AA8B 4

                Net Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum
172.18.1.2      172.18.2.2      170         0x80000009 0x00F137
172.18.2.2      172.18.2.2      679         0x80000039 0x008671

                Type-5 AS External Link States

Link ID         ADV Router      Age         Seq#       Checksum Tag
10.10.10.0      172.18.2.2      1466        0x80002338 0x00471C 0
10.10.10.61     172.18.2.2      1466        0x80002342 0x00CE4D 0
10.35.0.0       172.18.2.2      679         0x80000030 0x001099 0
10.36.0.0       172.18.2.2      1466        0x800079F2 0x00043E 0
10.37.1.0       172.18.2.2      1466        0x800079F2 0x00EC53 0
10.37.2.0       172.18.2.1      1126        0x80000929 0x00DD88 0
10.38.1.0       172.18.2.2      1466        0x800079F2 0x00E05E 0
64.230.170.178  172.18.2.1      1126        0x80000929 0x00CD45 0
68.67.38.192    172.18.2.2      1466        0x800079F2 0x0014FC 0
68.67.39.0      172.18.2.2      1466        0x800079F2 0x00EAD6 0
68.179.72.0     172.18.2.1      1126        0x80000929 0x00B9DC 0
68.179.72.0     172.18.2.2      679         0x80000030 0x00BD18 0
68.179.72.64    172.18.2.1      1126        0x80000929 0x00371F 0
68.179.72.192   172.18.2.1      1126        0x80000929 0x0032A3 0
68.179.84.209   172.18.2.1      1126        0x80000929 0x007EFA 0
68.179.84.210   172.18.2.1      1126        0x80000929 0x007404 0
172.16.14.0     172.18.2.1      1126        0x80000929 0x0014B8 0
172.22.21.166   172.18.2.1      1126        0x80000929 0x00FB1D 0
192.168.1.0     172.18.2.1      1126        0x80000929 0x006E88 0
192.168.15.0    172.18.2.1      1126        0x80000929 0x00EB8D 0
205.205.95.0    172.18.2.2      1466        0x800079F2 0x00066F 0
209.167.212.154 172.18.2.2      1466        0x800079F2 0x008502 0

            OSPF Router with ID (172.17.254.6) (Process ID 2)

                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
172.17.254.5    172.17.254.5    1972        0x8000094B 0x00D00D 2
172.17.254.6    172.17.254.6    2002        0x80007A4E 0x008ED6 2

                Net Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum
172.17.254.2    172.17.254.6    1243        0x80000039 0x00B04E
172.17.254.6    172.17.254.6    2002        0x80000008 0x00EA41

__________________________________________________________________
*local site*
#sho ip ospf database

            OSPF Router with ID (172.18.2.1) (Process ID 1)

                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
172.18.2.1      172.18.2.1      1914        0x8000094C 0x006CDD 27
172.18.2.2      172.18.2.2      209         0x80007A4A 0x00AA8B 4

                Net Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum
172.18.1.2      172.18.2.2      209         0x80000009 0x00F137
172.18.2.2      172.18.2.2      718         0x80000039 0x008671

                Type-5 AS External Link States

Link ID         ADV Router      Age         Seq#       Checksum Tag
10.10.10.0      172.18.2.2      1505        0x80002338 0x00471C 0
10.10.10.61     172.18.2.2      1505        0x80002342 0x00CE4D 0
10.35.0.0       172.18.2.2      718         0x80000030 0x001099 0
10.36.0.0       172.18.2.2      1505        0x800079F2 0x00043E 0
10.37.1.0       172.18.2.2      1505        0x800079F2 0x00EC53 0
10.37.2.0       172.18.2.1      1164        0x80000929 0x00DD88 0
10.38.1.0       172.18.2.2      1505        0x800079F2 0x00E05E 0
64.230.170.178  172.18.2.1      1164        0x80000929 0x00CD45 0
68.67.38.192    172.18.2.2      1505        0x800079F2 0x0014FC 0
68.67.39.0      172.18.2.2      1505        0x800079F2 0x00EAD6 0
68.179.72.0     172.18.2.1      1164        0x80000929 0x00B9DC 0
68.179.72.0     172.18.2.2      718         0x80000030 0x00BD18 0
68.179.72.64    172.18.2.1      1164        0x80000929 0x00371F 0
68.179.72.192   172.18.2.1      1164        0x80000929 0x0032A3 0
68.179.84.209   172.18.2.1      1164        0x80000929 0x007EFA 0
68.179.84.210   172.18.2.1      1164        0x80000929 0x007404 0
172.16.14.0     172.18.2.1      1164        0x80000929 0x0014B8 0
172.22.21.166   172.18.2.1      1164        0x80000929 0x00FB1D 0
192.168.1.0     172.18.2.1      1164        0x80000929 0x006E88 0
192.168.15.0    172.18.2.1      1164        0x80000929 0x00EB8D 0
205.205.95.0    172.18.2.2      1505        0x800079F2 0x00066F 0
209.167.212.154 172.18.2.2      1505        0x800079F2 0x008502 0

            OSPF Router with ID (172.17.254.5) (Process ID 2)

                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
172.17.254.5    172.17.254.5    2010        0x8000094B 0x00D00D 2
172.17.254.6    172.17.254.6    17          0x80007A4F 0x008CD7 2

                Net Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum
172.17.254.2    172.17.254.6    1282        0x80000039 0x00B04E
172.17.254.6    172.17.254.6    17          0x80000009 0x00E842

[chris.monk]

It doesn't look like you are receiving the static default route from your remote site.  Are you filtering your redistribution into OSPF?

If your remote site is how you get to the internet, is the default route on the remote 3750 with a next-hop of 10.31.0.1 going to the internet?

Can you post your complete config from the remote 3750?  Removing/censoring anything proprietary.

[Peter Paluch]

Hi Chris,

It seems that Andrew is using static default routes on his routes, not OSPF-learned static routes. In addition, you cannot redistribute a default route into OSPF - Cisco's implementation specifically makes sure that whatever redistribution is performed, the default route is not redistributed. The only way to inject a default route into OSPF is to use the default-information originate command (let's forget about S/TS/NSSA/NSSATS areas for now).

Best regards,

Peter

[chris.monk]

Peter is correct, I don't know how I was justifying my thinking when I typed that up.   

[Andrew Cormier]

Thanks  Chris and Peter.

I read this : http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00801ec9f0.shtml

what is interesting is  when I do show IP route 0.0.0.0 from the remote switch I see

show ip route 0.0.0.0

Routing entry for 0.0.0.0/0, supernet

  Known via "static", distance 1, metric 0, candidate default path

  Redistributing via ospf 1

  Routing Descriptor Blocks:

  * 10.31.0.1

      Route metric is 0, traffic share count is 1

So should I be adding default-information originate to the remote switch and then remove the two default gw routes from the local switch?

[chris.monk · Accepted solution]

Correct, you can do that with the statics in place still, checking the ospf database for the new defaults.  If they are there you can remove your statics.

[Andrew Cormier]

All is good. added default-information originate and saw 0.0.0.0 show up in the ospf db info (both sites)

removed both static routes.. tested.. all worked as it should.

Thanks again for all the help!!!