ICMPv6路由器通告RA（RouterAdvertisement）消息
IPv6路由器周期性发送ICMPv6路由器通告RA（RouterAdvertisement）消息，或者在收到路由请求RS（Router Solicitation）消息时回应ICMPv6 RA消息。ICMPv6 RA消息包括前缀和一些标志位的信息。
一、ICMPv6路由器通告消息报文格式
+0--------------7--------------15----------------------------31
| Type | Code | Checksum |
+-------------------------------------------------------------
| Cur Hop Limit |M|O| Reserved | Router Lifetime |
+-------------------------------------------------------------
| Reachable Time |
+-------------------------------------------------------------
| Retrans Time |
+-------------------------------------------------------------
| Options... |
+------------------------------------------------------------+
二、ICMPv6路由器通告消息报文格式解释
| 字段 | 长度 | 含义 |
|---|---|---|
| Type | 1字节 | 消息类型，此处值为134。 |
| Code | 1字节 | 该ICMPv6差错报文的始发者必须将该字段置为0，且接收端忽略该字段。 |
| Checksum | 2字节 | 用来在ICMPv6报文中检验数据和部分IPv6首部的完整性。 |
| Cur Hop Limit | 1字节 | 8位无符号整数。默认值应当放置在发出IP分组的IP首部的Hop Count字段中。 取0值意味着未(由该路由器)规定。 |
| M | 1比特 |
1位“管理地址配置”标记。当置1时，它指出地址可通过Dynamic Host Configuration协议获得。 如果M标记置1，则O标记为冗余，可以忽略，因为DHCPv6将返回所有可用配置信息。 |
| O | 1比特 |
1位“其他配置”标记。 当M=0且O=1时，指示其他配置信息可通过DHCPv6获得。例如，这类信息包括DNS相关信息或关于网络内其他服务器的信息。 如果M=0且O=0，指示没有信息可通过DHCPv6获得。 |
| Reserved | 6比特 | 6位未使用字段。它必须由发送者初始化为0，接收者必须忽略它。 |
| Router Lifetime | 2字节 | 16位无符号整数。与默认路由器关联的生存期，以秒为单位。最大值18.2小时。取0值的Lifetime指出路由器不是默认路由器并且不应当出现在默认路由器列表中。Router Lifetime仅适用于作为默认路由器的路由器应用；对包括在其他消息字段或选项中的信息不适用。需要对它们的信息规定时间限制的选项有它们自己的生存期字段。 |
| Reachable Time | 4字节 | 32位无符号整数。此时间以毫秒计，在收到可达性确认后节点假定该邻居是可到达的。它由Neighbor Unreachability Detection算法使用(参阅第7-3节)。此值为0意味着没有(由此路由器)作出规定。 |
| Retrans Timer | 4字节 | 32位无符号整数。重发的Neighbor Solicitation消息间隔时间，以毫秒计。由地址解析和Neighbor Unreachability Detection算法使用。此值为0意味着没有(由此路由器)作出规定。 |
| Options | 可变 | 选项
|
三、 ICMPv6路由器通告消息报文示例
Frame 1: 166 bytes on wire (1328 bits), 166 bytes captured (1328 bits)
Arrival Time: Sep 25, 2012 11:25:59.740076000
Epoch Time: 1348543559.740076000 seconds
[Time delta from previous captured frame: 0.000000000 seconds]
[Time delta from previous displayed frame: 0.000000000 seconds]
[Time since reference or first frame: 0.000000000 seconds]
Frame Number: 1
Frame Length: 166 bytes (1328 bits)
Capture Length: 166 bytes (1328 bits)
[Frame is marked: False]
[Frame is ignored: False]
[Protocols in frame: eth:ipv6:icmpv6]
[Coloring Rule Name: ICMP]
[Coloring Rule String: icmp || icmpv6]
Ethernet II, Src: RealtekS_88:5a:81 (00:e0:4c:88:5a:81), Dst: IPv6mcast_00:00:00:01 (33:33:00:00:00:01)
Destination: IPv6mcast_00:00:00:01 (33:33:00:00:00:01)
Address: IPv6mcast_00:00:00:01 (33:33:00:00:00:01)
.... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
.... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
Source: RealtekS_88:5a:81 (00:e0:4c:88:5a:81)
Address: RealtekS_88:5a:81 (00:e0:4c:88:5a:81)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
Type: IPv6 (0x86dd)
Internet Protocol Version 6, Src: fe80::2e0:4cff:fe88:5a81 (fe80::2e0:4cff:fe88:5a81), Dst: ff02::1 (ff02::1)
0110 .... = Version: 6
[0110 .... = This field makes the filter "ip.version == 6" possible: 6]
.... 0000 0000 .... .... .... .... .... = Traffic class: 0x00000000
.... 0000 00.. .... .... .... .... .... = Differentiated Services Field: Default (0x00000000)
.... .... ..0. .... .... .... .... .... = ECN-Capable Transport (ECT): Not set
.... .... ...0 .... .... .... .... .... = ECN-CE: Not set
.... .... .... 0000 0000 0000 0000 0000 = Flowlabel: 0x00000000
Payload length: 112
Next header: ICMPv6 (0x3a)
Hop limit: 255
Source: fe80::2e0:4cff:fe88:5a81 (fe80::2e0:4cff:fe88:5a81)
[Source SA MAC: RealtekS_88:5a:81 (00:e0:4c:88:5a:81)]
Destination: ff02::1 (ff02::1)
Internet Control Message Protocol v6
Type: Router Advertisement (134)
Code: 0
Checksum: 0xd11a [correct]
Cur hop limit: 0
Flags: 0x18
0... .... = Managed address configuration: Not set
.0.. .... = Other configuration: Not set
..0. .... = Home Agent: Not set
...1 1... = Prf (Default Router Preference): Low (3)
.... .0.. = Proxy: Not set
.... ..0. = Reserved: 0
Router lifetime (s): 7200
Reachable time (ms): 0
Retrans timer (ms): 0
ICMPv6 Option (Source link-layer address : 00:e0:4c:88:5a:81)
Type: Source link-layer address (1)
Length: 1 (8 bytes)
Link-layer address: RealtekS_88:5a:81 (00:e0:4c:88:5a:81)
ICMPv6 Option (MTU : 1500)
Type: MTU (5)
Length: 1 (8 bytes)
Reserved
MTU: 1500
ICMPv6 Option (Prefix information : fec0:0:0:4::/64)
Type: Prefix information (3)
Length: 4 (32 bytes)
Prefix Length: 64
Flag: 0xc0
1... .... = On-link flag(L): Set
.1.. .... = Autonomous address-configuration flag(A): Set
..00 0000 = Reserved: 0
Valid Lifetime: 172800
Preferred Lifetime: 1800
Reserved
Prefix: fec0:0:0:4:: (fec0:0:0:4::)
ICMPv6 Option (Prefix information : 2002:ac00:26e6:4::/64)
Type: Prefix information (3)
Length: 4 (32 bytes)
Prefix Length: 64
Flag: 0xd0
1... .... = On-link flag(L): Set
.1.. .... = Autonomous address-configuration flag(A): Set
..01 0000 = Reserved: 16
Valid Lifetime: 172800
Preferred Lifetime: 1800
Reserved
Prefix: 2002:ac00:26e6:4:: (2002:ac00:26e6:4::)
ICMPv6 Option (Route Information : Low 2002::/16)
Type: Route Information (24)
Length: 2 (16 bytes)
Prefix Length: 16
Flag: 0x18
...1 1... = Route Preference: Low (3)
000. .000 = Reserved: 0
Route Lifetime: 7200
Prefix: 2002:: (2002::)
发表评论