SmartSwitch Router User Reference Manual 91Chapter 6: IP Routing Configuration GuideConfiguring IP HelperYou can configure the SSR to forward UDP broadcast packets received on a given interfaceto all other interfaces or to a specified IP address. You can specify a UDP port number forwhich UDP broadcast packets with that destination port number will be forwarded. Bydefault, if no UDP port number is specified, the SSR will forward UDP broadcast packetsfor the following six services:• BOOTP/DHCP (port 67 and 68)• DNS (port 37)• NetBIOS Name Server (port 137)• NetBIOS Datagram Server (port 138)• TACACS Server (port 49)• Time Service (port 37)To configure a destination to which UDP packets will be forwarded, enter the followingcommand in Configure mode:Configuring Direct BroadcastYou can configure the SSR to forward all directed broadcast traffic from the local subnet toa specified IP address or all associated IP addresses. This is a more efficient method thandefining only one local interface and remote IP address destination at a time with the ip-helper command when you are forwarding traffic from more than one interface in thelocal subnet to a remote destination IP address.To forward all directed broadcast traffic to a specified IP address, enter the followingcommand in Configure mode:Configuring Denial of Service (DOS)By default, the SSR installs flows in the hardware so that packets sent as directedbroadcasts are dropped in hardware, if directed broadcast is not enabled on the interfacewhere the packet is received. You can disable this feature, causing directed broadcastSpecify local subnet interface,destination “helper” IPaddress, and UDP portnumber to forward.ip helper-address interface |all-interfaces []Forward directed broadcasttraffic.ip enable directed-broadcast interface|all
