Any ideas what I am doing wrong here?\n\nI am trying to set up a dial on demand ISDN link with one way calling only.\nI can get the link to come up and traffic to pass in one direction but no\ntraffic is returning over the link. According to Cisco the dialed router\nshould set up a dynamic mapping back over the ISDN link which it does.\n(confirmed with SH IP ROUTE with a /32 address). When using DEBUG IP TRAFFIC\nit becomes clear that the traffic is being sent to the BRI interface on\nreturn, but there is an encapsulation failure so it does not pass it\nback.over the link.\n\nI am using a 3620 and a 2522 and have tried it in both directions from clean\nload of routers. the 3620 is running IOS 12.0(8) and the 2522 12.0(17)\n\nThe config is as follows as it currently stands.\n\n2522\nip subnet-zero\nisdn switch-type basic-net3\n!\ninterface Loopback0\nip address 10.3.3.3 255.255.255.255\nno ip directed-broadcast\n!\ninterface BRI0\nip address 172.16.1.1 255.255.255.252\nno ip directed-broadcast\nencapsulation ppp\nisdn switch-type basic-net3\nip classless\nip route 0.0.0.0 0.0.0.0 172.16.1.2 permanent\n\n3620\nip subnet-zero\nisdn switch-type basic-net3\n!\ninterface Loopback0\nip address 10.4.4.4 255.255.255.255\nno ip directed-broadcast\n!\ninterface BRI1/0\nip address 172.16.1.2 255.255.255.252\nno ip directed-broadcast\nencapsulation ppp\ndialer map ip 172.16.1.1 21\ndialer-group 1\nisdn switch-type basic-net3\n!\nip classless\nip route 0.0.0.0 0.0.0.0 172.16.1.1 permanent\n!\ndialer-list 1 protocol ip permit\n\nPlease note I have tried pointing the default route to the local, remote IP\naddresses of the BRI interface and also to the BRI interface itself. The\nonly difference I have found is that I have to point it to the remote\naddress to bring the link up.\n\nWhat have I missed?\n\nThanks\n\nToby\n\nP.S. I am using a ISDN PBX to test this hence the two digit dialing\nsequence. Not a simulator.