5 replies to this topic

[ciberkot]

Hi,

again BGP in LAB.
eg. in the LAB2 from IEWB we should configure the BGP session between routers, but there is no any requirements which prefixes should they anounce. One topic asks to configure to anounce to one BBx the summary routes.
Is it corect in this case case to not announce internal networks to BB's ?

[taner]

Hi,

again BGP in LAB.
eg. in the LAB2 from IEWB we should configure the BGP session between routers, but there is no any requirements which prefixes should they anounce. One topic asks to configure to anounce to one BBx the summary routes.
Is it corect in this case case to not announce internal networks to BB's ?

Hi

The internal networks are 132.1.x.0/24 , the question says that advertise only one prefix tu BB2 so you need to summarize your internal network to BB2.First you need to add at least one spesific prefix to your bgp table to summarize them on R5.
R5
#router bgp 200
#network 132.1.5.0 mask 255.255.255.0

if you check your your bgp table you will see this prefix is being advertised to BB2 ,but it says that advertise one route representing your entire major network.

#aggregate-address 132.1.0.0 255.255.0.0 summary-only

with the summary-only keyword you will suppress spesific subnets ,and you will only advertise summarized subnet.After this config BB2 will see only one prefix from R5 132.1.0.0/16 .Then from every router in your internal network ping BB2 prefixes ,there should be two way communication.


In this lab there is no igp between BB2 and R5 ,if there were igp between them and full ip reachability to all igp prefixes(I mean redistribution is correct ) ,you would not advertise or summarize your internal network to BB2.Be careful to the requirements,every lab may be different.

[ciberkot]

In this lab there is no igp between BB2 and R5 ,if there were igp between them and full ip reachability to all igp prefixes(I mean redistribution is correct ) ,you would not advertise or summarize your internal network to BB2.Be careful to the requirements,every lab may be different.

with BB2 the things are clear, what I mean there is no any information (we're still talking about lab2 ) about advetising the internal networks to BB1 or BB3, does it mean that one should not advetise the internal networks to BB1 or BB3?

[taner]

with BB2 the things are clear, what I mean there is no any information (we're still talking about lab2 ) about advetising the internal networks to BB1 or BB3, does it mean that one should not advetise the internal networks to BB1 or BB3?
[/quote]


it says "Configure your network to reflect this policy ,but do not allow any other routers within your network to see the summary route".R5 has 2 ebgp peerings with As300 ,one is R3 the other one is R4.So,on R5 you need to filter the summary route to R3 and R4(As300),and they are not going to see this route.If they dont see the summary route they can not advertise to BB1 or BB3.You need to understand this policy requirement indirectly.

[taner]

with BB2 the things are clear, what I mean there is no any information (we're still talking about lab2 ) about advetising the internal networks to BB1 or BB3, does it mean that one should not advetise the internal networks to BB1 or BB3?

One more thing ;

With BB1 and BB3 you are running IGP ,and if you do redistribution correctly you do not need to advertise your internal network to them...but with BB2 you are not runnşng IGP ,for full IP reachability you should advertise your internal network to BB2.(but the important thing is the requirement)

[ciberkot]

with BB2 the things are clear, what I mean there is no any information (we're still talking about lab2 ) about advetising the internal networks to BB1 or BB3, does it mean that one should not advetise the internal networks to BB1 or BB3?

One more thing ;

With BB1 and BB3 you are running IGP ,and if you do redistribution correctly you do not need to advertise your internal network to them...but with BB2 you are not runnşng IGP ,for full IP reachability you should advertise your internal network to BB2.(but the important thing is the requirement)

hm, you're right, exactly, we're running IGP with BB1 and BB3. but then what the reason to configure the BGP for them if no prefixes are advetising via BGP process?
OK, it's not the real life, it's the lab