OSPF LSAck报文
OSPF LSAck（Link State Acknowledgment）用来对接收到的LSU报文进行确认。内容是需要确认的LSA的Header（一个LSAck报文可对多个LSA进行确认）。
一、OSPF LSAck报文格式
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
+---------------+---------------+-------------------------------+
| Version | 5 | Packet length |
+---------------+---------------+-------------------------------+
| Router ID |
+---------------------------------------------------------------+
| Area ID |
+-------------------------------+-------------------------------+
| Checksum | AuType |
+-------------------------------+-------------------------------+
| Authentication |
+---------------------------------------------------------------+
| Authentication |
+---------------------------------------------------------------+
| |
+- -+
| |
+- An LSA Header -+
| |
+- -+
| |
+- -+
| |
+---------------------------------------------------------------+
| ... |
二、OSPF LSAck报文格式含义
| 字段 | 长度 | 含义 |
|---|---|---|
| Version | 1字节 | 版本，OSPF的版本号。对于OSPFv2来说，其值为2。 |
| Packet length | 2字节 | OSPF报文的总长度，包括报文头在内，单位为字节。 |
| Router ID | 4字节 | 发送该报文的路由器标识。 |
| Area ID | 4字节 | 发送该报文的所属区域。 |
| Checksum | 2字节 | 校验和，包含除了认证字段的整个报文的校验和。 |
| AuType | 2字节 | 验证类型，值有如下几种表示：
|
| Authentication | 8字节 |
鉴定字段，其数值根据验证类型而定：
MD5验证数据添加在OSPF报文后面，不包含在Authenticaiton字段中。 |
| An LSA Header | 可变 | 通过LSA的头部信息确认收到该LSA。 |
三、OSPF LSAck报文示例
Frame 53680: 78 bytes on wire (624 bits), 78 bytes captured (624 bits)
Encapsulation type: Ethernet (1)
Arrival Time: Jul 22, 2014 18:12:29.242735000
[Time shift for this packet: 0.000000000 seconds]
Epoch Time: 1406023949.242735000 seconds
[Time delta from previous captured frame: 0.095087000 seconds]
[Time delta from previous displayed frame: 0.095087000 seconds]
[Time since reference or first frame: 3888368.615394000 seconds]
Frame Number: 53680
Frame Length: 78 bytes (624 bits)
Capture Length: 78 bytes (624 bits)
[Frame is marked: False]
[Frame is ignored: False]
[Protocols in frame: eth:ethertype:ip:ospf]
[Coloring Rule Name: OSPF State Change]
[Coloring Rule String: ospf.msg != 1]
Ethernet II, Src: Novell_40:64:00 (1b:00:00:40:64:00), Dst: 00:0b:04:00:ff:ff (00:0b:04:00:ff:ff)
Destination: 00:0b:04:00:ff:ff (00:0b:04:00:ff:ff)
Address: 00:0b:04:00:ff:ff (00:0b:04:00:ff:ff)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Source: Novell_40:64:00 (1b:00:00:40:64:00)
[Expert Info (Warn/Protocol): Source MAC must not be a group address: IEEE 802.3-2002, Section 3.2.3(b)]
[Source MAC must not be a group address: IEEE 802.3-2002, Section 3.2.3(b)]
[Severity level: Warn]
[Group: Protocol]
Address: Novell_40:64:00 (1b:00:00:40:64:00)
.... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
.... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
Type: IP (0x0800)
Internet Protocol Version 4, Src: 10.41.22.2 (10.41.22.2), Dst: 224.0.0.5 (224.0.0.5)
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: 64
Identification: 0x4cea (19690)
Flags: 0x00
0... .... = Reserved bit: Not set
.0.. .... = Don't fragment: Not set
..0. .... = More fragments: Not set
Fragment offset: 0
Time to live: 1
Protocol: OSPF IGP (89)
Header checksum: 0x6b8b [validation disabled]
[Good: False]
[Bad: False]
Source: 10.41.22.2 (10.41.22.2)
Destination: 224.0.0.5 (224.0.0.5)
[Source GeoIP: Unknown]
[Destination GeoIP: Unknown]
Open Shortest Path First
OSPF Header
Version: 2
Message Type: LS Acknowledge (5)
Packet Length: 44
Source OSPF Router: 10.96.0.40 (10.96.0.40)
Area ID: 1.1.1.1 (1.1.1.1)
Checksum: 0x225b [correct]
Auth Type: Null (0)
Auth Data (none): 0000000000000000
LSA Header
.000 1110 0001 0000 = LS Age (seconds): 3600
0... .... .... .... = Do Not Age Flag: 0
Options: 0x02 (E)
0... .... = DN: Not set
.0.. .... = O: Not set
..0. .... = DC: Demand Circuits are NOT supported
...0 .... = L: The packet does NOT contain LLS data block
.... 0... = NP: NSSA is NOT supported
.... .0.. = MC: NOT Multicast Capable
.... ..1. = E: External Routing Capability
.... ...0 = MT: NO Multi-Topology Routing
LS Type: Summary-LSA (IP network) (3)
Link State ID: 10.20.20.1 (10.20.20.1)
Advertising Router: 10.41.22.1 (10.41.22.1)
Sequence Number: 0x80000003
Checksum: 0x5a77
Length: 28
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