bit bucket into the routers - Null0

[ohareka70]

Hello,

I’d like to put a bit bucket into the routers. I think i can save bandwidth and security things by dropping any rubbish.

ON ROUTERS WITHOUT STATIC REDISTRIBUTION

int Null0
exit

ip route 0.0.0.0 0.0.0.0 NUll0

ON ROUTERS WITH STATIC REDISTRIBUTION

int Null0
exit

access-list 99 deny 0.0.0.0 255.255.255.255
access-list 99 permit <IP SUBNET> <INVERSE MASK> of route

route-map NULL-ROUTE permit 10
match ip address 99

router ospf 1
redistribute static subnets route-map NULL-ROUTE

ip route 0.0.0.0 0.0.0.0 NUll0

Anyone done this before and have any experience i can draw on.

regards

Kevin

[Edison Ortiz · Accepted solution]

On the first example, you don't need to create a Null0 interface in order to drop packets with the static route.

Are you planning to drop the packets that are destined for the internet? I'm assuming you will have more specific subnets in your routing table.

On the second example, the ACL 99 is not going to process the 2nd line since the first line will simply deny any subnets. I'm not sure the intent of this ACL.

If you are looking to block the default from being redistributed into OSPF, do the following:

ip prefix-list Quad0 permit 0.0.0.0/0

route-map NULL0 deny 5

match ip prefix-list Quad0

!

route-map NULL0 permit 10

!

Regards,

[ohareka70]

I dont want to drop packets destined for the internet so i'll be careful with that one.

I think i'll give this one a go.

ip prefix-list Quad0 permit 0.0.0.0/0

route-map NULL0 deny 5

match ip prefix-list Quad0

!

route-map NULL0 permit 10

!

thanks,

kevin

[Edison Ortiz]

Reviewing your route-map once again, it really won't do much as you can't redistribute the Quad0 into OSPF.

OSPF will only originate a Quad0 by using the command 'default-information originate' (if the Quad0 is in the RIB) or 'default-information originate always' (if you want to originate the Quad0 when not in RIB).

If this router is being used to take you into the internet, a default static route pointing to Null0 will drop all packets.