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Updated:May 10, 2016
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This document describes a new CLI, which tracks the presence of a Point-to-Point Protocol (PPP) session over a dialer interface.
Dialer interface is used widely in Digital Subscriber Line (DSL) world, in different type of deployments like Point-to-Point Protocol over Ethernet (PPPoE), Point-to-Point Protocol over Asynchronous Transfer Mode (PPPoA) and so on. Dialer interface always stay up irrespective of the PPP session on top of it is up or down. One known problem with this behavior is that it can cause black hole in routing in cases where you have multiple outgoing connections, unless you use some additional features such as Internet Protocol Service Level Agreement (IP SLA) tracking to check the reachability over dialer interface.
A new CLI dialer down-with-vInterface has been introduced in recent IOS versions brings the dialer interface down when the PPP session goes down.
A configuration snippet from a DSL Router:
interface Dialer1 ip address negotiated encapsulation ppp dialer pool 1 ppp chap hostname email@example.com ppp chap password 0 cisco
Dialer interface is in up state, even though the PPPoE session is down.
Router#show pppoe session 1 client session
Uniq ID PPPoE RemMAC Port VT VA State SID LocMAC VA-st Type N/A 58 00c1.64d5.41d1 Gi0/1 Di1 N/A PADISNT 0006.f657.67b1
Router#show interface dialer1 Dialer1 is up, line protocol is up (spoofing) Hardware is Unknown Internet address will be negotiated using IPCP MTU 1500 bytes, BW 56 Kbit/sec, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation PPP, LCP Closed, loopback not set Keepalive set (10 sec) DTR is pulsed for 1 seconds on reset Last input never, output never, output hang never Last clearing of "show interface" counters 00:49:48 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo Output queue: 0/40 (size/max) 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 0 packets input, 0 bytes 538 packets output, 7524 bytes CLIENT(config-if)
You can add the new CLI under Dialer interface configuration as shown: