11-12-2011 12:21 PM - edited 03-07-2019 03:21 AM
Hi everybody
Please consider the following set-up:
R1---Rip------R2---ospf area 1---------R3--------ospf area 0-------R2
In our example, R2 is ASBR. R2 has following table;
C 10.10.1.0/8 directly connected loopback 1
R 10.10.10.0/24 via R1
R 10.10.20.0/24 Via R2
C 199.199.199.0/24 ( connected to R3)
When I used the command" Summary-address 0.0.0.0 0.0.0.0 " on R2( ASBR), and do show running-config, I get the following:
summary-address 0.0.0.0 0.0.0.0 do-no advertise.
When checked the option as :
summary-address 0.0.0.0 0.0.0.0 ?
not-advertise Do not advertise when translating OSPF type-7 LSA
tag Set tag
<cr>
I am unable to understand it; would someone break it down for me ?
My second question is when i used the command : summary -address 0.0.0.0 0.0.0.0 on ASBr, does it not summarize all the routes present in our routing table?
=======================================
Quote from my CCNP routing book
Enterprises typically use default route in two different cases;
1) To direct remote-site routers at the edge of t he Enterprise network to send all packets towards the core ,
2) To direct traffic on all enterprise routers towards an internet-facing routers.
Engineers could achieve both of these goals by using route summarization with the area range and summary address commands.
My question is how these commands ( area x range , summary-address)can be used to flood default route in ospf domain?
Thanks and have a great weekend
Solved! Go to Solution.
11-13-2011 12:17 AM
Hi sarah,
before I answer your question about your default route query, allow me to just refresh the place of use of
( area x range, summary-address )
area x range is used on ABR to summarise the individual subnets.
summary-address is used on ASBR to summarise the external individual subnets.
Within the ospf process if you want to flood the default route you need the default-informatino originate command.
The only time you can getaway without using that command and still generate a default route is where ABR generates a default route when you use the stub areas features.
OSPF does not support the summary-address 0.0.0.0 0.0.0.0 command. Please see the below link to support this statement.
http://www.cisco.com/en/US/docs/ios/12_3/iproute/command/reference/ip2_s3g.html#wp1041286
The way to generate a default route on a ASBR or an ABR is to use default-informatin originate.
http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9e.shtml#t38
Does the book specificaly say that you can use are x range and summary-address default route?
HTH
Kishore
11-13-2011 02:39 AM
Hi sarah
to add to the above posts
the range used for LSA type 3 summarizations also known as inter area summary
for example
10.10.1.0/24 --area 10---R1---area 0 ---- R2
R1 can summarize area 10 to be seen by R2 as /8 using area range command
while the summary-address is used by the ASBR to summarize LSAtype 5 or in the case of Not so stuby area ASBR/ABR from type 7 to 5
however default route works diffrrently in OSPF which is as describe by other posters above
also area type can inject the default route by default in some cases
hope this help
plz rate the helpful posts
11-12-2011 12:29 PM
Hi,
to inject a default-route in OSPF you must use default-information originate command.
Regards.
Alain
11-12-2011 01:52 PM
Thank Alain
I am not cleared as to how these commands ( area x range, summary-address ) can be used to flood default route.
.
11-13-2011 12:17 AM
Hi sarah,
before I answer your question about your default route query, allow me to just refresh the place of use of
( area x range, summary-address )
area x range is used on ABR to summarise the individual subnets.
summary-address is used on ASBR to summarise the external individual subnets.
Within the ospf process if you want to flood the default route you need the default-informatino originate command.
The only time you can getaway without using that command and still generate a default route is where ABR generates a default route when you use the stub areas features.
OSPF does not support the summary-address 0.0.0.0 0.0.0.0 command. Please see the below link to support this statement.
http://www.cisco.com/en/US/docs/ios/12_3/iproute/command/reference/ip2_s3g.html#wp1041286
The way to generate a default route on a ASBR or an ABR is to use default-informatin originate.
http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9e.shtml#t38
Does the book specificaly say that you can use are x range and summary-address default route?
HTH
Kishore
11-13-2011 02:39 AM
Hi sarah
to add to the above posts
the range used for LSA type 3 summarizations also known as inter area summary
for example
10.10.1.0/24 --area 10---R1---area 0 ---- R2
R1 can summarize area 10 to be seen by R2 as /8 using area range command
while the summary-address is used by the ASBR to summarize LSAtype 5 or in the case of Not so stuby area ASBR/ABR from type 7 to 5
however default route works diffrrently in OSPF which is as describe by other posters above
also area type can inject the default route by default in some cases
hope this help
plz rate the helpful posts
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide