12-01-2008 08:37 AM - edited 03-04-2019 12:33 AM
Hi Guys,
What are the differences among the following statements:
1)
router ospf 1
summary-address 10.0.0.0 255.0.0.0 tag 11122
redistribute ospf 2 metric 5000 subnets route-map TAG-Question
route-map TAG-Question permit 10
match ip address TAG_ACL
2)
router ospf 1
summary-address 10.0.0.0 255.0.0.0
redistribute ospf 2 metric 5000 subnets route-map TAG-Question
route-map TAG-Question permit 10
match ip address TAG_ACL
set tag 11122
3)
router ospf 1
summary-address 10.0.0.0 255.0.0.0 tag 11122
redistribute ospf 2 metric 5000 subnets route-map TAG-Question
route-map TAG-Question permit 10
match ip address TAG_ACL
set tag 11122
According to my understanding no 1 & 2 does the same thing,please correct me if I am wrong. However I am confused with the no.3.
Regards,
Solved! Go to Solution.
12-01-2008 10:09 AM
Hello Iqbal,
here you have two statements in each OSPF routing process:
a redistribute OSPF 2 + options
a summary -address + options
the results can be different depending on what routes are present in OSPF 2 DB (and in the IP routing table otherwise they are not redistributed into OSPF1).
If all OSPF 2 subnets are within net 10/8 the first option will:
create and propagate a summary address 10/8 with route-tag 11122 in the route tag field of the LSA external type 5 with seed metric 5000. (subnets are suppressed by the summary-address command they are in the router DB but they are not sent out in OSPF1 domain)
if all OSPF 2 subnets are within net 10/8 second option will:
create and propagate a summary address 10/8 with route-tag 2 in the route tag field of the LSA external type 5 with seed metric 5000.
Can you see the difference ?
if OSPF 2 DB and routing table contains prefixes out of net 10/8 and permitted by the ACL:
all the subnets in 10/8 will be suppressed and the summary 10/8 is created as described above.
Prefixes out of net 10/8 will:
have a route-tag of 2 in case 1)
have a route-tag of 11122 in case 2)
in 3) being the route-tag value the same in both commands:
net 10/8 will have route-tag 11122
if other prefixes out of 10/8 are imported by ospf2 into ospf1 they also have route-tag 11122
Hope to help
Giuseppe
12-01-2008 10:09 AM
Hello Iqbal,
here you have two statements in each OSPF routing process:
a redistribute OSPF 2 + options
a summary -address + options
the results can be different depending on what routes are present in OSPF 2 DB (and in the IP routing table otherwise they are not redistributed into OSPF1).
If all OSPF 2 subnets are within net 10/8 the first option will:
create and propagate a summary address 10/8 with route-tag 11122 in the route tag field of the LSA external type 5 with seed metric 5000. (subnets are suppressed by the summary-address command they are in the router DB but they are not sent out in OSPF1 domain)
if all OSPF 2 subnets are within net 10/8 second option will:
create and propagate a summary address 10/8 with route-tag 2 in the route tag field of the LSA external type 5 with seed metric 5000.
Can you see the difference ?
if OSPF 2 DB and routing table contains prefixes out of net 10/8 and permitted by the ACL:
all the subnets in 10/8 will be suppressed and the summary 10/8 is created as described above.
Prefixes out of net 10/8 will:
have a route-tag of 2 in case 1)
have a route-tag of 11122 in case 2)
in 3) being the route-tag value the same in both commands:
net 10/8 will have route-tag 11122
if other prefixes out of 10/8 are imported by ospf2 into ospf1 they also have route-tag 11122
Hope to help
Giuseppe
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