Network Advertisement and Summarization
I have seen in some configuration where they Advertise the Network with a prefix different than the Interface IP mask.
They also summarize the network different than the interface IP mask.
Example:
Let's say I have R1 connected to R2 through serial interfaces on each router.
R1 serial interface has Ip address 10.10.10.1/24 and R2 serial interface has ip address 10.10.10.2/24
when Network is advertised in EIGRP for instance, they use the command:
EIGRP 90
Network 10.0.0.0
** I believe The Network command above will by default add a mask of /8 , it is like typing 255.0.0.0
which is different than /24 mask of the serial interface.
So what would be the impact in that case?
another scenario is Summarization,example :
Interface serial 1/0
ip summary-address EIGRP 90 10.10.0.0 255.255.0.0
I see the summarization is based on /16 , so how this would impact the /24 configured on the serial interfaces ?
Thank you
They also summarize the network different than the interface IP mask.
Example:
Let's say I have R1 connected to R2 through serial interfaces on each router.
R1 serial interface has Ip address 10.10.10.1/24 and R2 serial interface has ip address 10.10.10.2/24
when Network is advertised in EIGRP for instance, they use the command:
EIGRP 90
Network 10.0.0.0
** I believe The Network command above will by default add a mask of /8 , it is like typing 255.0.0.0
which is different than /24 mask of the serial interface.
So what would be the impact in that case?
another scenario is Summarization,example :
Interface serial 1/0
ip summary-address EIGRP 90 10.10.0.0 255.255.0.0
I see the summarization is based on /16 , so how this would impact the /24 configured on the serial interfaces ?
Thank you
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Sometimes they add the Wild card mask and sometimes not.
if interface is configured with 10.10.10.1/24 and the Network is advertised without mask, then there is no Impact if I understand your comment
EIGRP 90
Network 10.0.0.0
(This implicitly will look just for the first octet to be matched, the rest of the octets do not matter)
****for the Summary , let's say we have a bunch of Loopback interfaces :
2.2.2.1/24
2.2.2.2/24
2.2.2.3/24
2.2.2.4/24
if I am not wrong ,The IP summary has to match the first 3 octets otherwise , the router receiving the summary routes will not be able to reach the loopbacks… Correct ?
it has to be:
ip summary-address EIGRP 90 2.0.0.0 255.255.255.0
and Not:
ip summary-address EIGRP 90 2.0.0.0 255.255.0.0