當(dāng)在接口使用ip helper-address命令，路由器會(huì)前傳接收到的UDP廣播報(bào)文到指定服務(wù)器地址
創(chuàng)新互聯(lián)專注于湟源企業(yè)網(wǎng)站建設(shè),響應(yīng)式網(wǎng)站建設(shè),電子商務(wù)商城網(wǎng)站建設(shè)。湟源網(wǎng)站建設(shè)公司,為湟源等地區(qū)提供建站服務(wù)。全流程按需定制，專業(yè)設(shè)計(jì)，全程項(xiàng)目跟蹤，創(chuàng)新互聯(lián)專業(yè)和態(tài)度為您提供的服務(wù)
Lab_B(config)#interface f0/0
Lab_B(config-if)#ip helper-address 192.168.254.251
下表列出了前傳的數(shù)據(jù)包類型
| Port or Protocol | Meaning | On by Default |
| <0–65535> | Port number (create your own) | |
| biff | Biff (mail notification, comsat, 512) | |
| bootpc | Bootstrap Protocol (BOOTP) client (68) | X |
| bootps | Bootstrap Protocol (BOOTP) server (67) | X |
| discard | Discard (9) | |
| DNSix | DNSIX security protocol auditing (195) | |
| domain | Domain Name Service (DNS) (53) | X |
| echo | Echo (7) | |
| isakmp | Internet Security Association and Key Management Protocol (ISAKMP) (500) | |
| mobile-ip | Mobile IP registration (434) | |
| nameserver | IEN116 name service (obsolete, 42) | |
| netbios-dgm | NetBios datagram service (138) | X |
| netbios-ns | NetBios name service (137) | X |
| netbios-ss | NetBios session service (139) | |
| ntp | Network Time Protocol (NTP) (123) | |
| pim-auto-rp | PIM Auto-RP (496) | |
| rip | Routing Information Protocol (RIP) (router, in.routed, 520) |
這些默認(rèn)的前傳類型，可以通過(guò)下面的命令關(guān)閉，只開啟bootps UDP 67，來(lái)提高路由器的安全性
Lab_B(config)#no ip forward-protocol udp 69
Lab_B(config)#no ip forward-protocol udp 53
Lab_B(config)#no ip forward-protocol udp 37
Lab_B(config)#no ip forward-protocol udp 137
Lab_B(config)#no ip forward-protocol udp 138
Lab_B(config)#no ip forward-protocol udp 68
Lab_B(config)#no ip forward-protocol udp 49
