Here is the senerio..
AS 100 >> AS 200 >> 300. That is, AS 100 is directly connected to AS 200 which directly connected to AS 300. All network inside each AS as directly connected. 2 networks each. No routing protocol is configured. Now, I can ping and see device in networks in AS 100 from AS 200 and vice verser. I can see all routes from AS 300 but cannot get to any network in AS 100 from AS 300. Question is, how do you configure bgp to see network in different AS that are not directly connected. If I do sh ip bgp and show ip route, I can see all route to all XXX and all network. Thanks you all.

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Paste your router's config. I don't see any reason why you can't ping the network in AS100 from AS300. Is your config similar to this one:

AS100
networks : 10.10.10.0/24, 10.10.100.0/24
router bgp 100
network 10.10.10.0 mask 255.255.255.0
network 10.10.100.0 mask 255.255.255.0
neighbor XXXX.XXXX.XXXX.XX remote-as 200

AS200
networks : 50.50.50.0/24, 50.50.150.0/24
router bgp 200
network 50.50.50.0 mask 255.255.255.0
network 50.50.150.0 mask 255.255.255.0
neighbor XXXX.XXXX.XXXX.XX remote-as 100
neighbor XXXX.XXXX.XXXX.XX remote-as 300

AS300
networks: 70.70.70.0/24, 70.70.170.0/24
router bgp 300
network 70.70.70.0 mask 255.255.255.0
network 70.70.170.0 mask 255.255.255.0
neighbor XXXX.XXXX.XXXX.XX remote-as 200

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Your conf is similar to mine except I don't have the mask specified in the network command. I'm at work now, I will paste my config when I get home. Please check site late on tonight, if you have some time.

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A lot of people forget to do this when configuring BGP:
When you make a configuration change with respect to a neighbor for which a peer relationship has been established, be sure to reset the BGP session with that neighbor. To reset the session, at the system prompt, issue the clear ip bgp EXEC command specifying the IP address of that neighbor.

I know I have forgotten on more than one occasion.

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Yes I do reset the bgp nei everytime changes are made. I think bgp is a very complecated protocol. I'm working on iot everyday, so I know one day I will be a bgp guru. Thanks to you all.

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