I have a setup of R1 -- R2. I configured the OSPF network type as broadcast in R1 and P2P in R2.
I still see the neighbourship comes up. Will the network type is not checked in the initial hello message?
If so, what are the consequences of keeping different network types in OSPF links?. Thanks for your feedback
Look this good article:https://packetlife.net/blog/2008/jun/19/ospf-network-types/
In shot words.
P2P: do not scale well, if your network interface is /24 it will be propagated as /32
BROADCAST: will use multicast to neighbor statement and scale very well.
For the adjacency to be successful, the hello and dead timer must be the same.
In the types of OSPF that you set these parameters are the same, so you have adjacency.
The other OSPF types these parameters are not equal, so you would not have adjacency.
Check those indicated in this link:
Hello timer and dead timer in point-to-point and broadcast are the same.. in this case he will have adjacency.. but the difference as i said.. point-to-point will show in routing table a route /32 :)
in my experience:
a network type mismatch between broadcast and P2P can cause routing problems.
The broadcast side would like to elect a DR /BDR and will wait up to wait time 40 seconds to do that.
After that the R1 broadcast side will start to send OSPF hellos every 10 seconds stating:
DR = my own OSPF RID example 10.1.1.1.1
BDR= 0.0.0.0 ! means unknown
neighbor seen : R2 LAN IP address
The two devices can reach the two way status ( I see your IP address in respective hello messages), but they cannot reach full adjacency:
R1 will create an LSA type 2 with LSA id = R1's LAN interface to R2 with an emptly list of neighbors
R1 will create its own Router LSA for the area the link is in.
R2 will only create a Router LSA for the area the common link is in.
R1 expects to receive updates on ALLOSPFDR 22.214.171.124
R2 uses only allospf routers on link 126.96.36.199
on point to point links we see in show ip ospf neighbor
on broadcast links possible cases are:
the device is not a DR/BDR:
For a DR/BDR the show ip ospf neigh will tell:
the use of point to point OSPF network type (both ends) started in service provider networks for single dedicated high speed links to avoid creation of un necessary L2 network type.
As a further step for IPv4 p2p links the right to use /31 subnets has been added.
The Choice of the DR and BDR in a broadcast environment must be careful and you need to play with OSPF priority to avoid to have the same devices elected as DR/BDR for their highest OSPF RID.
Another way to say resources on user facing Vlans/subnets is to use
router ospf 10
Where Vlan50 is the SVI of a multilayer switch.
For access multilayer switches :
the passive-interface default can be used
an NSSA area can be used for each site a L3 or L2 port channel can be used between the multilayer switches.
uplinks are in area 0.0.0.0 of course
Hope to help
as i said, adjacency will be form without issue. Like exemple below;
and routes will be available on both routers
but it is not common in environments.