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Cisco CCNP / BCSI Exam Tutorial: Broadcasts Plus theCisco CCNP / BCSI Test Tutorial: Broadcasts As well as the IP Helper-Deal with CommandAlthough routers accept Visit the website and crank out broadcasts, they don't forward them. This can be very a dilemma each time a broadcast should reach a device for instance a DHCP or TFTP server that’s on a single facet of the router with other subnets on the other aspect. If a Laptop tries to Track down a DNS server that has a broadcast, the broadcast are going to be stopped through the router and will never get towards the DNS server. By configuring the ip helper-address command within the router, UDP broadcasts including this will be translated right into a unicast with the router, producing the communication possible. The command should be configured within the interface that may be obtaining the broadcasts.R1(config)#int e0R1(config-if)#ip helper-handle ? A.B.C.D IP spot addressR1(config-if)#ip helper-address 100.1.one.twoNow, you could be asking yourself if this command covers all UDP companies. Sorry, you’re not acquiring off that straightforward! The command does ahead eight widespread UDP services broadcasts, nevertheless. TIME, port 37TACACS, port forty nineDNS, port fifty threeBOOTP/DHCP Server, port 67BOOTP/DHCP Consumer, port sixty eightTFTP, port sixty nineNetBIOS identify company, port 137NetBIOS datagram provider, port 138That’s gonna protect most situations where by the ip helper-address command are going to be helpful, but How about All those predicaments where by the printed you would like forwarded is not really on this list? You should use the ip forward-protocol command to include any UDP port amount to your listing.On top of that, to get rid of protocols within the default checklist, use the no ip forward-protocol command. In the next case in point, we’ll add the Network Time Protocol port on the forwarding listing though eradicating the NetBIOS ports. Try to remember, You should utilize IOS Assistance to receive an index of typically filtered ports!R1(config)#ip ahead-protocol udp ? <0-65535> Port quantity biff Biff (mail notification, comsat, 512) bootpc Bootstrap Protocol (BOOTP) shopper (sixty eight) bootps Bootstrap Protocol (BOOTP) server (67) discard Discard (9) dnsix DNSIX safety protocol auditing (195) area Domain Name Company (DNS, fifty three) echo Echo (seven) isakmp Internet Security Association and Crucial Administration Protocol (500) cellular-ip Cellular IP registration (434) nameserver IEN116 identify service (obsolete, 42) netbios-dgm NetBios datagram company (138) netbios-ns NetBios title assistance (137) netbios-ss NetBios session support (139) ntp Network Time Protocol (123) pim-vehicle-rp PIM Auto-RP (496) rip Routing Information Protocol (router, in.routed, 520) snmp Straightforward Network Administration Protocol (161) snmptrap SNMP Traps (162) sunrpc Solar Remote Treatment Contact (111) syslog Technique Logger (514) tacacs TAC Obtain Control System (forty nine) converse Converse (517) tftp Trivial File Transfer Protocol (69) time Time (37) who Who assistance (rwho, 513) xdmcp X Display Supervisor Command Protocol (177