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Hey

Ive got 2 6509 \w MSFC2 connected to each other with about 15 VLANs. Most
VLANs are setup on both MSFCs except for a few specifics.

To keep traffic between the 2 switches on a specific VLAN I use ip ospf cost
1 on the interswitch VLAN3 and 'ip ospf cost 2' on all other VLANs 1,2.
This is an administrative hassle bc whenever a new VLAN is created we have
to remember to do ip ospf cost 2 or load sharing occurs . This extra step
is tedious, plus I really dont need OSPF running on most of these interfaces
anyway (I think ) because 1. there are no other OSPF routers on these VLANs
and 2. since both MSFCs have connected interfaces they can route traffic
from the interswitch VLAN to the destination VLAN. I have HSRP config'd on
all VLAN interfaces that are on both MSFCs.

If I were to remove all the ip ospf cost cmd's, add passive interface
default and no passive interface vlan3 to both router ospf configs would
there be any downsides ? I see lots of benefits like - dont have to worry
about rogue routers on end user vlan poisioning route tables , - less CPU
util since no SPF algo running for all these passive interfaces, -less admin
work (no more need for ip ospf cost 2) ... I cant think of any downsides...

Take a look at this example
http://box1.theglens.net/net/ip-ospf-issue.gif


Thanks

Timo

timo wrote:

> Hey
>
> Ive got 2 6509 \w MSFC2 connected to each other with about 15 VLANs. Most
> VLANs are setup on both MSFCs except for a few specifics.
>
> To keep traffic between the 2 switches on a specific VLAN I use ip ospf cost
> 1 on the interswitch VLAN3 and 'ip ospf cost 2' on all other VLANs 1,2.
> This is an administrative hassle bc whenever a new VLAN is created we have
> to remember to do ip ospf cost 2 or load sharing occurs . This extra step
> is tedious, plus I really dont need OSPF running on most of these interfaces
> anyway (I think ) because 1. there are no other OSPF routers on these VLANs
> and 2. since both MSFCs have connected interfaces they can route traffic
> from the interswitch VLAN to the destination VLAN. I have HSRP config'd on
> all VLAN interfaces that are on both MSFCs.
>
> If I were to remove all the ip ospf cost cmd's, add passive interface
> default and no passive interface vlan3 to both router ospf configs would
> there be any downsides ? I see lots of benefits like - dont have to worry
> about rogue routers on end user vlan poisioning route tables , - less CPU
> util since no SPF algo running for all these passive interfaces, -less admin
> work (no more need for ip ospf cost 2) ... I cant think of any downsides...
>
> Take a look at this example
> http://box1.theglens.net/net/ip-ospf-issue.gif
>
>
> Thanks
>
> Timo
That is exactly what I would do. Works great.

In article < >,
says...
> Hey
>
> Ive got 2 6509 \w MSFC2 connected to each other with about 15 VLANs. Most
> VLANs are setup on both MSFCs except for a few specifics.
>
> To keep traffic between the 2 switches on a specific VLAN I use ip ospf cost
> 1 on the interswitch VLAN3 and 'ip ospf cost 2' on all other VLANs 1,2.
> This is an administrative hassle bc whenever a new VLAN is created we have
> to remember to do ip ospf cost 2 or load sharing occurs . This extra step
> is tedious, plus I really dont need OSPF running on most of these interfaces
> anyway (I think ) because 1. there are no other OSPF routers on these VLANs
> and 2. since both MSFCs have connected interfaces they can route traffic
> from the interswitch VLAN to the destination VLAN. I have HSRP config'd on
> all VLAN interfaces that are on both MSFCs.
>
> If I were to remove all the ip ospf cost cmd's, add passive interface
> default and no passive interface vlan3 to both router ospf configs would
> there be any downsides ? I see lots of benefits like - dont have to worry
> about rogue routers on end user vlan poisioning route tables , - less CPU
> util since no SPF algo running for all these passive interfaces, -less admin
> work (no more need for ip ospf cost 2) ... I cant think of any downsides...
>
> Take a look at this example
> http://box1.theglens.net/net/ip-ospf-issue.gif

Not really. But you don't have any redundant connections between the
two. Even that won't matter in some cases (though it's not a good
design practice).

--

hsb

"Somehow I imagined this experience would be more rewarding" Calvin
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