https://supportforums.cisco.com/ja/document/103001
ともあれOSPF、エリア概説のあたりから。
・LSAはふらッでぃんぐされるもの。
・ふらッでぃんぐは、ある程度の範囲に制限されなくてはならない。
(そんなん規模次第)
・だからエリアの概念
・ネットわーく情報をダダ漏れにするのではなく集約するからこそエリア(ABR/ASBR)
・ちっちゃくするもの3つ
1. りんくすてーとでーたべーす(LSDB)
2. しょーてすとぱすふぁすと計算頻度
3. ルーティングテーブルサイズ
CPU使用率やメモリ使用率についての言及があってごもっともではあるが、根本はやはり2.。ちゅーか、キャリアじゃあるまいし、そうそうルーティングに影響与えるような変更は "起こらないように最初から" 設計する。もちろん、仕事にありがちなのは既にメチャクチャな設計を後からどうにかする、だが。
・ご推奨はエリア0バックボーン＆各エリアは/24＆ABRで/16集約
・OSPFはろー
OSPFヘッダ以下の中身はこんな。
OSPF Header
Version: 2
Message Type: Hello Packet (1)
Packet Length: 48
Source OSPF Router: 192.168.235.169 (192.168.235.169)
Area ID: 0.0.1.21 (0.0.1.21)
Checksum: 0x00f6 [correct]
Auth Type: Null (0)
Auth Data (none): 0000000000000000
OSPF Hello Packet
Network Mask: 255.255.255.0 (255.255.255.0)
Hello Interval [sec]: 10
Options: 0x12 (L, E)
0... .... = DN: Not set
.0.. .... = o: Not set
..0. .... = DC: Demand Circuits are NOT supported
...1 .... = L: The packet contains 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
Router Priority: 1
Router Dead Interval: 172.19.19.254 (172.19.19.254)
Backup Designated Router: 172.19.19.2 (172.19.19.2)
Active Neighbor: 172.19.19.2(172.19.19.2)
OSPF LLS Data Block
Checsum: xfff6
LLS Data Length: 12 bytes
Extended options TLV
Type: 1
Length: 4
Options: 0x00000000 (LR)
.... .... .... .... .... .... .... ..0. = RS: Restart Signal (RS-bit) is NOT set
.... .... .... .... .... .... .... ...1 = LR: LSTB Resynchronization (LR-bit) is SET
OSPFが稼働しているルータ(172.19.19.2)に新たに1台OPSFルータ(172.19.19.254)があがってくるとこのように。タイプ4アップデートと、タイプ5アックナレッジがとぶ。
No. Time Source Destination Protocol Length Info
125 118.799626000 172.19.19.2 224.0.0.5 OSPF 94 Hello Packet
Frame 125: 94 bytes on wire (752 bits), 94 bytes captured (752 bits) on interface 0
Ethernet II, Src: CiscoInc_c8:28:7c (00:26:99:c8:28:7c), Dst: IPv4mcast_05 (01:00:5e:00:00:05)
Internet Protocol Version 4, Src: 172.19.19.2 (172.19.19.2), Dst: 224.0.0.5 (224.0.0.5)
Open Shortest Path First
No. Time Source Destination Protocol Length Info
126 119.299539000 172.19.19.2 224.0.0.5 OSPF 122 LS Update
Frame 126: 122 bytes on wire (976 bits), 122 bytes captured (976 bits) on interface 0
Ethernet II, Src: CiscoInc_c8:28:7c (00:26:99:c8:28:7c), Dst: IPv4mcast_05 (01:00:5e:00:00:05)
Internet Protocol Version 4, Src: 172.19.19.2 (172.19.19.2), Dst: 224.0.0.5 (224.0.0.5)
Open Shortest Path First
No. Time Source Destination Protocol Length Info
127 119.301449000 172.19.19.254 224.0.0.5 OSPF 98 LS Update
Frame 127: 98 bytes on wire (784 bits), 98 bytes captured (784 bits) on interface 0
Ethernet II, Src: CiscoInc_99:b8:15 (2c:54:2d:99:b8:15), Dst: IPv4mcast_05 (01:00:5e:00:00:05)
Internet Protocol Version 4, Src: 172.19.19.254 (172.19.19.254), Dst: 224.0.0.5 (224.0.0.5)
Open Shortest Path First
No. Time Source Destination Protocol Length Info
128 119.331618000 172.19.19.2 224.0.0.5 OSPF 94 LS Update
Frame 128: 94 bytes on wire (752 bits), 94 bytes captured (752 bits) on interface 0
Ethernet II, Src: CiscoInc_c8:28:7c (00:26:99:c8:28:7c), Dst: IPv4mcast_05 (01:00:5e:00:00:05)
Internet Protocol Version 4, Src: 172.19.19.2 (172.19.19.2), Dst: 224.0.0.5 (224.0.0.5)
Open Shortest Path First
No. Time Source Destination Protocol Length Info
132 121.303699000 172.19.19.2 224.0.0.5 OSPF 98 LS Acknowledge
Frame 132: 98 bytes on wire (784 bits), 98 bytes captured (784 bits) on interface 0
Ethernet II, Src: CiscoInc_c8:28:7c (00:26:99:c8:28:7c), Dst: IPv4mcast_05 (01:00:5e:00:00:05)
Internet Protocol Version 4, Src: 172.19.19.2 (172.19.19.2), Dst: 224.0.0.5 (224.0.0.5)
Open Shortest Path First
No. Time Source Destination Protocol Length Info
133 121.305369000 172.19.19.254 224.0.0.5 OSPF 198 LS Acknowledge
Frame 133: 198 bytes on wire (1584 bits), 198 bytes captured (1584 bits) on interface 0
Ethernet II, Src: CiscoInc_99:b8:15 (2c:54:2d:99:b8:15), Dst: IPv4mcast_05 (01:00:5e:00:00:05)
Internet Protocol Version 4, Src: 172.19.19.254 (172.19.19.254), Dst: 224.0.0.5 (224.0.0.5)
Open Shortest Path First
No. Time Source Destination Protocol Length Info
134 121.361454000 172.19.19.254 224.0.0.5 OSPF 94 Hello Packet
Frame 134: 94 bytes on wire (752 bits), 94 bytes captured (752 bits) on interface 0
Ethernet II, Src: CiscoInc_99:b8:15 (2c:54:2d:99:b8:15), Dst: IPv4mcast_05 (01:00:5e:00:00:05)
Internet Protocol Version 4, Src: 172.19.19.254 (172.19.19.254), Dst: 224.0.0.5 (224.0.0.5)
Open Shortest Path First
OSPFなエントリはまだまだ続く。
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