question about redistribution

[Dr.X]

hi ,

assume i have a router with two domains as below :

---------OSPF domain -----------------------192.168.1.10/24-<ROUTER> 10.10.10.10/24-------------------------------EIGRP domain

assume under eigrp 1

network 10.0.0.0

no auto summary

================

under ospf

redistribute eigrp 1  subnets

redistribute connected metric 200

====================

my question is ,

as u see, the network 10.10.10.0/24 was matched by two redistribution commands

one by connetced , and the other by network command .

my question is ,

with wt command the network 10.10.10.0/24 will be redistributed into ospf doamin >???

i mean how to the prioruity  is given ?

will it be redistributed with metric 200 "" redistribute connected "" command or by the source metric ""netowrk command""

???/

regards

[wjguest28]

I didn't look this up, taken from memory so take it for what it is worth.

The redistribute command with the subnets keyword will redistribute eigrp learned route. IE routes that are not connected.

Redistribute connected routes - redistribute directly connected subnets

Sent from Cisco Technical Support iPhone Apps

[Dr.X]

hi ,

thanks for ur reply , ,

im understanding ur reply ,

but im asking ,

the network 10 is macted by two redistribution commands

one  by redistribute connected , and the other is network  command ,

with wt command i will be redistributed ??

regaeds

[Giuseppe Larosa]

Hello Ahmed,

the network command leads to the generation of an OSPF internal route that is preferred over an OSPF external route.

So for the connected interface(s) matching the network ... area command OSPF internal routes should be generated with network ..area command overriding the redistribute connected.

There is also another way to see this: the network .. area command is more specific then the redistribute connected so it is preferred.

Note:

it is not correct to say that network ,,, area command redistributes into OSPF, it generates internal routes and interfaces matching the network command run OSPF and can build neighborships over them

Hope to help

Giuseppe

[Dr.X]

hi ,

sorry for type ,

my question againa :

hi ,

assume i have a router with two domains as below :

---------OSPF  domain -----------------------192.168.1.10/24-10.10.10.10/24 ------------------------EIGRP domain

assume under eigrp 1

network 10.0.0.0

no auto summary

================

under ospf

network 192.168.1.0 0.0.0.255 area 0

redistribute eigrp 1  subnets

redistribute connected metric 200

====================

as u see above ,

into ospf i want to redistribute the eigrp doamin and the connwected subnets

note that the network 10.10.10.0/24 is both , in eigrp doamin and  from connected subnets ,

my question is ,

with wt redistribution command will take the effect of redistributin the 10.10.10.0 network in the ospf domain ??

regards

[Giuseppe Larosa]

Hello Ahmed,

>> with wt redistribution command will take the effect of redistributin the 10.10.10.0 network in the ospf domain ?

on device 10.10.10.0/24 is first of all a connected route I would expect the route to be injected by the redistribute connected command.

You can easily check what happens:

You can use

show ip ospf database external 10.10.10.0 

to see the LSA type 5 generated

look at the metric field if it is 200 the route has been generated by red conn command.

You can also use

show ip route 10.10.10.0

and look at the lines

redistributed by ...

and advertised by ....

it should declare what is doing

You can use a

clear ip ospf proc

to run the test multiple times to see if there is competition between the two redistribution methods.

IF the result is always the same, it is deterministic and there is a rule to solve the competition.

If the result varies there is competition between the two redistribution methods and this would be bad news as it does not provide consistency over time.

The only doubt can be the order of redistribution commands in router ospf configuration, can this be a criteria used to solve the competition?

I don't think so.

Hope to help

Giuseppe

[Dr.X]

good ,

why redistribute connected command is  preferred than network command ??

regards

[Giuseppe Larosa · Accepted solution]

Hello Ahmed,

the IP subnet 10.10.10.0/24 is injected in OSPF domain

or by redistribute connected

or by redistribute eigrp 1

With redistribute connected that should be preferred

For prefix 192.168.1.0   network ... area command should take over on redistribute connected as I have explained in my first post in this thread

Hope to help

Giuseppe

[Dr.X]

hi ,

Giuseppe Larosa

in summary ,

the redistribute connected is more prefered than network command ,

thats wt i want to know

thanks very much

regards

[Giuseppe Larosa]

Hello Ahmed,

>> the redistribute connected is more prefered than network command ,

No, I didn't mean this.

Please refer to my previous post.

Best Regards

Giuseppe

[Dr.X]

i mean subnet which was matched by two redisribute statements ,"network" & " redsitribute connetced"

the redistribute connected is will take effect &  network command  will see to be ignored  to this subnet

that wt i understood

[Giuseppe Larosa]

Hello Ahmed,

we have discussed two different cases in this thread

a)   IP subnet 10.10.10.0   no network command present in router ospf, two redistribute statements that can inject the route into OSPF domain

redistribute connected should take over on redistribute eigrp 1 subnets  (actually to be tested,  a procedure to perform the test using clear ip osp proc,  show ip ospf database external 10.10.10.0 and show ip route 10.10.10.0 has been described)

b)  IP subnet 192.168.1.0

here there is a network command under router ospf and the redistribute connected

in this latter case OSPF network ... area command overrides redistribute connected and an internal route is generated.

So as you see in second case it is network command preferred over redistribute connected

Consider that network ... area has multiple effects: it allows to advertise an internal OSPF route and enables OSPF on matching interfaces so that OSPF relationships can be built. 

This is different from redistribute connected that does not provide OSPF activation on interfaces.

For better route control I can add that

network ... area

+ passive-interface interface type x/y

is to be preferred over redistribute connected

The second method generates OSPF external routes that cannot be filtered in an OSPF domain ( not selectively)

The first method allows to generate internal routes without enabling OSPF in matching interfaces.

This is useful on client facing Vlans where speaking and listening to OSPF messages is not needed.

Internal routes can be filtered selectively at area borders if needed.

But this is a different matter.

Hope to help

Giuseppe