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lambert
Long time Member
Long time Member
Topic Author
Posts: 548
Joined: Fri Jul 23, 2010 1:09 am

OSPF change prefix len on connected subnet, subnet not adv

Sun Apr 15, 2012 9:12 am

RouterOS 5.14 RB493G

We had IP address x.y.z.36/28 configured on a bridge interface. Also have a.b.c.9/29 on the same bridge interface.

We split the subnet into 2 /29s. The x.y.z.36 address stayed on the bridge interface, but I changed the /28 to /29 via winbox. I hit the up arrow beside the network address entry in the IP address dialog box to clear it. In 4.x I needed to clear the network and broadcast address when changing subnets or the didn't change to match the new IP and prefix length. I hit the Ok button and went on with life. I was still able to access the hosts in that subnet with the new longer prefix. I was connected to the router.

Unfortunately, the OSPF neighbor at the office, Cisco, no longer had a route for x.y.z.32/28 or x.y.z.32/29. Six hours later I was notified that hosts on that x.y.z.32/29 subnet were unreachable.

When I logged in, I disabled the IP address, waited 10 seconds, and enabled the IP address. The subnet was then seen in the routing table of the device at the office.

Unfortunately, I did not log into the other MikroTik routers which have OSPF neighbor relationships with this router.

Is this a known issue?

[gw1.gvh] /routing ospf> export compact
# apr/15/2012 06:02:38 by RouterOS 5.14
# software id = XXXXXXXXXX
#
/routing ospf instance
set [ find default=yes ] redistribute-connected=as-type-1 redistribute-static=as-type-1 \
    router-id=a.b.c.9
/routing ospf interface
add network-type=broadcast passive=yes
add authentication=md5 authentication-key=md5authkeysecret interface=ether1 network-type=\
    point-to-point
add authentication=md5 authentication-key=md5authkeysecret interface=ether2 network-type=\
    point-to-point
add authentication=md5 authentication-key=md5authkeysecret interface=lan_bridge \
    network-type=broadcast
/routing ospf network
add area=backbone network=a.b.c.0/24
add area=backbone network=a.b.d.0/24
add area=backbone network=a.b.e.0/24
add area=backbone disabled=yes network=x.y.z.0/22
 
Ascii
newbie
Posts: 32
Joined: Sat Apr 25, 2009 11:15 pm
Location: Quito, Ecuador

Re: OSPF change prefix len on connected subnet, subnet not a

Sun Apr 15, 2012 1:05 pm

I have the same problem before.

I can reproduce the problem.
If I change my network 10.255.255.0/24 to 10.255.255.0/25 using winbox the LSA disappear.
The problem only happen with external routes (redistribute connected/static)

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