HDLC協議有關命令與配置
HDLC是CISCO路由器使用的缺省協議，一臺新路由器在未指定封裝協議時默認使用HDLC封裝。本博文將為您詳細介紹HDLC協議的有關命令及配置。
HDLC協議是一種簡單、高效的點到點鏈路協議，主要用于點到點連接的路由器間的通信。HDLC協議有 Cisco HDLC 和 ISO DHLC 兩種，兩者不能兼容。
銳捷路由器的同步串行口默認封裝Cisco HDLC，所以銳捷路由器可以和Cisco路由器直接相連，但如果把銳捷路由器和不支持Cisco HDLC的路由器相連，就需要采用其它協議(如PPP)。
1.有關命令
端口設置
注:1.以下給出一個顯示Cisco同步串口狀態的例子.
Router#show interface serial 0
Serial 0 is up, line protocol is up
Hardware is MCI Serial
Internet address is 150.136.190.203, subnet mask is 255.255.255.0
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255
Encapsulation HDLC, loopback not set, keepalive set (10 sec)
Last input 0:00:07, output 0:00:00, output hang never
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
Five minute input rate 0 bits/sec, 0 packets/sec
Five minute output rate 0 bits/sec, 0 packets/sec
16263 packets input, 1347238 bytes, 0 no buffer
Received 13983 broadcasts, 0 runts, 0 giants
2 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 2 abort
22146 packets output, 2383680 bytes, 0 underruns
0 output errors, 0 collisions, 2 interface resets, 0 restarts
1 carrier transitions
2. 舉例
設置如下：
Router1:
interface Serial0
ip address 192.200.10.1 255.255.255.0
clockrate 1000000
Router2:
interface Serial0
ip address 192.200.10.2 255.255.255.0
!
3. 舉例使用E1線路實現多個64K專線連接.
相關命令:
注: 1. 當鏈路為T1時,channel-group編號為0-23, Timeslot范圍1-24; 當鏈路為E1時, channel-group編號為0-30, Timeslot范圍1-31.
2.使用show controllers e1觀察controller狀態,以下為幀類型為crc4時controllers正常的狀態.
Router# show controllers e1
e1 0/0 is up.
Applique type is Channelized E1 - unbalanced
Framing is CRC4, Line Code is HDB3 No alarms detected.
Data in current interval (725 seconds elapsed):
0 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs
Total Data (last 24 hours) 0 Line Code Violations, 0 Path Code Violations,
0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs
以下例子為E1連接3條64K專線, 幀類型為NO-CRC4,非平衡鏈路,路由器具體設置如下:
shanxi#wri t
Building configuration...
Current configuration:
!
version 11.2
no service udp-small-servers
no service tcp-small-servers
!
hostname shanxi
!
enable secret 5 $1$XN08$Ttr8nfLoP9.2RgZhcBzkk/
enable password shanxi
!
!
ip subnet-zero
!
controller E1 0
framing NO-CRC4
channel-group 0 timeslots 1
channel-group 1 timeslots 2
channel-group 2 timeslots 3
!
interface Ethernet0
ip address 133.118.40.1 255.255.0.0
media-type 10BaseT
!
interface Ethernet1
no ip address
shutdown
!
interface Serial0:0
ip address 202.119.96.1 255.255.255.252
no ip mroute-cache
!
interface Serial0:1
ip address 202.119.96.5 255.255.255.252
no ip mroute-cache
!
interface Serial0:2
ip address 202.119.96.9 255.255.255.252
no ip mroute-cache
!
no ip classless
ip route 133.210.40.0 255.255.255.0 Serial0:0
ip route 133.210.41.0 255.255.255.0 Serial0:1
ip route 133.210.42.0 255.255.255.0 Serial0:2
!
line con 0
line aux 0
line vty 0 4
password shanxi
login
!
end
3、配置keepalive時間
HDLC每隔10秒鐘就互相發送鏈路探測的協商報文(KeepAlive報文)，用于探查鏈路是否中斷，每次收發的報文按序號遞增，序號失序則鏈路中斷。當接口連續3次(數據包速率超過1000packets/s時為6次)沒有收到對方對自己的遞增序號的確認時，HDLC協議就把鏈路狀態由Up轉變為Down，鏈路將不可用。
HDLC協議可配置的參數只有Keepalive的間隔時間，缺省值是10秒。可以根據鏈路的流量來修改這個值。
1、配置keepalive時間：
Router(config)#interface interface-id
Router(config-if)#keepalive seconds
interface 命令用于指定要配置的接口，必須是Serial口，interface-id是接口號。
keepalive 命令設置keepalive時間，seconds是以秒為單位的時間值。
2、忽略keepalive探查：
Router(config)#interface interface-id
Router(config-if)#no keepalive
使用 no keepalive 命令表示不進行HDLC鏈路狀態探查，即不發送keepalive報文，也不處理收到的keepalive報文。
配置舉例：
R1>enable R1#configure terminal R1(config)#interface s0/0 R1(config-if)#encapsulation hdlc R1(config-if)#keepalive 15
R2>enable R2#configure terminal R2(config)#interface s0/0 R2(config-if)#encapsulation hdlc R2(config-if)#keepalive 15
注意：你必須保證相連兩端的keepalive時間相同。
