Cisco CCNP / BCSI Examination Tutorial: Broadcasts And also the IP Helper-Deal with Command
Though routers settle for and produce broadcasts, they don't forward them. This may be rather an issue any time a broadcast ought to get to a tool like a DHCP or TFTP server that’s on 1 facet of a router with other subnets on one other facet.
If a Personal computer makes an attempt to Identify a DNS server by using a broadcast, the published might be stopped via the router and won't ever get to the DNS server. By configuring the ip helper-deal with command over the router, UDP broadcasts like this may 사설사이트 be translated into a unicast by the router, creating the conversation achievable. The command ought to be configured around the interface that could be getting the broadcasts.
R1(config)#int e0
R1(config-if)#ip helper-deal with ?
A.B.C.D IP destination handle
R1(config-if)#ip helper-address 100.1.one.two
Now, you may well be pondering if this command covers all UDP providers. Sorry, you’re not getting off that uncomplicated! The command does http://www.bbc.co.uk/search?q=토토사이트 ahead eight typical UDP support broadcasts, nevertheless.
TIME, port 37
TACACS, port forty nine
DNS, port 53
BOOTP/DHCP Server, port 67
BOOTP/DHCP Consumer, port sixty eight
TFTP, port sixty nine
NetBIOS name support, port 137
NetBIOS datagram support, port 138
That’s about to go over most eventualities the place the ip helper-address command will be useful, but How about People scenarios in which the printed you require forwarded just isn't on this listing? You should use the ip forward-protocol command so as to add any UDP port quantity towards the listing.
Additionally, to remove protocols with the default checklist, use the no ip ahead-protocol command. In the subsequent illustration, we’ll add the Community Time Protocol port towards the forwarding listing even though eradicating the NetBIOS ports. Bear in mind, You need to use IOS Support to acquire a list of frequently filtered ports!
R1(config)#ip ahead-protocol udp ?
<0-65535> Port range
biff Biff (mail notification, comsat, 512)
bootpc Bootstrap Protocol (BOOTP) shopper (sixty eight)
bootps Bootstrap Protocol (BOOTP) server (67)
discard Discard (nine)
dnsix DNSIX stability protocol auditing (195)
area Domain Identify Assistance (DNS, fifty three)
echo Echo (7)
isakmp Net Stability Association and Important Management Protocol (five hundred)
mobile-ip Mobile IP registration (434)
nameserver IEN116 name support (out of date, 42)
netbios-dgm NetBios datagram service (138)
netbios-ns NetBios name support (137)
netbios-ss NetBios session service (139)
ntp Community Time Protocol (123)
pim-automobile-rp PIM Automobile-RP (496)
rip Routing Info Protocol (router, in.routed, 520)
snmp Basic Community Management Protocol (161)
snmptrap SNMP Traps (162)
sunrpc Sunlight Distant Procedure Phone (111)
syslog Procedure Logger (514)
tacacs TAC Access Management Program (forty nine)
discuss Discuss (517)
tftp Trivial File Transfer Protocol (sixty nine)
time Time (37)
who Who service (rwho, 513)
xdmcp X Show Manager Manage Protocol (177)