PIM C-RP Advertisement报文格式
当PIM-SM网络中使用动态RP时，配置了C-RP的路由器周期性的向BSR发送PIM C-RP Advertisement消息，通告希望服务的组范围。C-RP Advertisement消息只在PIM-SM中使用。
一、C-RP Advertisement报文消息格式
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-------+-------+---------------+-------------------------------+
|PIM Ver| Type | Reserved | Checksum |
+-------+-------+---------------+-------------------------------+
| Prefix-cnt | Priority | Holdtime |
+---------------+---------------+-------------------------------+
| Group Address [1] |
+---------------------------------------------------------------+
| .... |
+---------------------------------------------------------------+
| Group Address [N] |
+---------------------------------------------------------------+
二、C-RP Advertisement报文消息格式解释
| 字段 | 长度 | 说明 |
|---|---|---|
| PIM Ver | 4比特 | PIM版本，值为2。 |
| Type | 4比特 | 消息类型，值为8。 |
| Reserved | 8比特 | 保留。发送者将其设置为0，接收者忽略此字段。 |
| Checksum | 16比特 | 校验和。 |
| Prefix-Cnt | 8比特 | 组播地址前缀值。 |
| Priority | 8比特 | C-RP优先级。 |
| Holdtime | 16比特 | Advertisement消息的老化时间。 |
| RP-Address | 32比特 | C-RP地址。 |
| Group Address | 32比特 | 组播组地址。 |
三、PIM C-RP Advertisement消息报文示例
Frame 1: 68 bytes on wire (544 bits), 68 bytes captured (544 bits)
Encapsulation type: Ethernet (1)
Arrival Time: Jan 1, 1970 08:00:00.058557000
[Time shift for this packet: 0.000000000 seconds]
Epoch Time: 0.058557000 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: 68 bytes (544 bits)
Capture Length: 68 bytes (544 bits)
[Frame is marked: False]
[Frame is ignored: False]
[Protocols in frame: eth:ethertype:vlan:ethertype:ip:pim]
Ethernet II, Src: 54:89:98:74:e4:04 (54:89:98:74:e4:04), Dst: 54:89:98:f6:45:64 (54:89:98:f6:45:64)
Destination: 54:89:98:f6:45:64 (54:89:98:f6:45:64)
Address: 54:89:98:f6:45:64 (54:89:98:f6:45:64)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Source: 54:89:98:74:e4:04 (54:89:98:74:e4:04)
Address: 54:89:98:74:e4:04 (54:89:98:74:e4:04)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 6, CFI: 0, ID: 423
110. .... .... .... = Priority: Voice, < 10ms latency and jitter (6)
...0 .... .... .... = CFI: Canonical (0)
.... 0001 1010 0111 = ID: 423
Type: IP (0x0800)
Trailer: 00000000a2c62cb3
Internet Protocol Version 4, Src: 10.0.0.42 (10.0.0.42), Dst: 10.0.0.43 (10.0.0.43)
Version: 4
Header Length: 20 bytes
Differentiated Services Field: 0xc0 (DSCP 0x30: Class Selector 6; ECN: 0x00: Not-ECT (Not ECN-Capable Transport))
1100 00.. = Differentiated Services Codepoint: Class Selector 6 (0x30)
.... ..00 = Explicit Congestion Notification: Not-ECT (Not ECN-Capable Transport) (0x00)
Total Length: 42
Identification: 0x0acb (2763)
Flags: 0x00
0... .... = Reserved bit: Not set
.0.. .... = Don't fragment: Not set
..0. .... = More fragments: Not set
Fragment offset: 0
Time to live: 255
Protocol: PIM (103)
Header checksum: 0x598c [validation disabled]
[Good: False]
[Bad: False]
Source: 10.0.0.42 (10.0.0.42)
Destination: 10.0.0.43 (10.0.0.43)
[Source GeoIP: Unknown]
[Destination GeoIP: Unknown]
Protocol Independent Multicast
0010 .... = Version: 2
.... 1000 = Type: Candidate-RP-Advertisement (8)
Reserved byte(s): 00
Checksum: 0x493a [correct]
PIM options
Prefix-count: 1
Priority: 0
Holdtime: 150s
RP: 10.0.0.42 (10.0.0.42)
Group 0: 224.0.0.0/4
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