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Cisco CCNP / BCSI Exam Tutorial: Broadcasts And TheCisco CCNP / BCSI Test Tutorial: Broadcasts And The IP Helper-Handle CommandWhile routers acknowledge and create broadcasts, they don't ahead them. This can be rather a difficulty when a broadcast should reach a tool for instance a DHCP or TFTP server that’s on just one aspect of the router with other subnets on one other side. If a Computer system tries to Track down a DNS server that has a broadcast, the published are going to be stopped via the router and will never get towards the DNS server. By configuring the ip helper-address command around the router, UDP broadcasts including this tends to be translated right into a unicast by the router, earning the conversation attainable. The command should be configured around the interface that could be acquiring the broadcasts.R1(config)#int e0R1(config-if)#ip helper-handle ? A.B.C.D IP vacation spot handleR1(config-if)#ip helper-handle one hundred.one.one.2Now, you may be asking yourself if this command addresses fast all UDP solutions. Sorry, you’re not finding off that straightforward! The command does ahead eight common UDP assistance broadcasts, however. TIME, port 37TACACS, port forty nineDNS, port fifty threeBOOTP/DHCP Server, port 67BOOTP/DHCP Customer, port 68TFTP, port sixty nineNetBIOS title company, port 137NetBIOS datagram service, port 138That’s intending to deal with most scenarios wherever the ip helper-address command are going to be helpful, but How about those cases in which the broadcast you require forwarded just isn't on this listing? You can use the ip ahead-protocol command to incorporate any UDP port range to the checklist.On top of that, to eliminate protocols within the default listing, use the no ip forward-protocol command. In the following instance, we’ll add the Community Time Protocol port to the forwarding record though eradicating the NetBIOS ports. Bear in mind, You should utilize IOS Assist to obtain a list of commonly filtered ports!R1(config)#ip forward-protocol udp ? <0-65535> Port quantity biff Biff (mail notification, comsat, 512) bootpc Bootstrap Protocol (BOOTP) client (68) bootps Bootstrap Protocol (BOOTP) server (67) discard Discard (nine) dnsix DNSIX protection protocol auditing (195) area Domain Identify Company (DNS, fifty three) echo Echo (seven) isakmp Web Safety Association and Essential Administration Protocol (five hundred) cell-ip Cell IP registration (434) nameserver IEN116 name assistance (obsolete, forty two) netbios-dgm NetBios datagram assistance (138) netbios-ns NetBios identify provider (137) netbios-ss NetBios session provider (139) ntp Community Time Protocol (123) pim-automobile-rp PIM Vehicle-RP (496) rip Routing Facts Protocol (router, in.routed, 520) snmp Basic Community Management Protocol (161) snmptrap SNMP Traps (162) sunrpc Solar Remote Procedure Simply call (111) syslog Procedure Logger (514) tacacs TAC Accessibility Command Program (forty nine) speak Speak (517) tftp Trivial File Transfer Protocol (sixty nine) time Time (37) who Who services (rwho, 513) xdmcp X Exhibit Manager Management Protocol (177