[KEDUIT] 클라우드 컴퓨팅과 보안솔루션을 활용한 DC 엔지니어 양성교육 - Day37

1. 서론

    오늘은 CEF에 대하여 배워보았다.

2. 본론

1. Cisco IOS

1. CEF

//CEF(Cisco Express Forwarding)
- 대부분 Cisco Router의 Default Switching type
- 위 사진처럼 FIB, Adj Table을 사용(CPU 처리 x)
- Trie 구조 사용(Tree x)

//FIB(Forwarding Information Base) : FIB is known by the name of CEF table. FIB table learns the routing information from the IP Routing Table and tracks the next-hop for all routes. So while the Adjacency table manages layer 2 information, the CEF table manages the layer 3 forwarding information. The adjacency table maintains Layer 2 information for next hops listed in the FIB.

장점:
The adjacency table can be built separately from the Cisco Express Forwarding table, allowing both to build without process switching any packets.

The MAC header rewrite used to forward a packet is not stored in cache entries, so changes in a MAC header rewrite string do not require invalidation of cache entries.

You can point directly to the forwarding information, rather than to the recursed next hop, in order to resolve recursive routes.

Essentially, all cache aging is eliminated, and the cache is pre-built based on the information contained in the routing table and ARP cache. There is no need to process switch any packet to build a cache entry.

CEF 처리과정 -
Once the packets arrive at the router, its layer 2 information is stripped off. This is a normal procedure that happens whenever a frame is accepted to a layer 3 device
The router looks up the destination using the CEF table. Note that even 1st packet router does not reach the Router CPU. CEF handles all the packets as they enter the interface.
Router finds the corresponding adjacency table entry.
The router then adds the corresponding layer 2 information (found in the adjacency table) back to the packet and forwards the packets.

3. 결론

    하루종일 문서들만 봤더니 어지럽다.

4. 참고자료

1. 자료

1. 문웅호, 정보통신망

2. Cisco Docs

1. ARP
2. CDP / VLAN
3. Frame Relay
4. Static Routing
5. VLAN
6. VTP
7. Routed Port
8. AD
9. Route Selection
10. FHRP
11. HSRP
12. DHCP
13. DNS
14. STP
15. NAT
16. EtherChannel
17. DTP
18. RIP
19. NTP
20. Offset List
21. Password Encryption
22. ACL
23. CAR Attack
24. Broadcast
25. Port Assignments
26. IPv6 Static Routing
27. HSRP for IPv6
28. Clock Rate
29. DHCPv6 Guard
30. EIGRP
31. Express Forwarding
32. Routing and Switching
33. Load Balancing
34. Ping, Traceroute
35. Load Balancing
36. Fast Switching
37. CEF

3. Linux

1. Linux Directory Structure
2. File Types in Linux
3. fstab
4. Vim Cheat Sheet

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클라우드 엔지니어를 꿈꾸며 공부를 시작한 초보 엔지니어입니다. 틀린점 또는 조언해주실 부분이 있으시면 친절하게 댓글 부탁드립니다. 방문해 주셔서 감사합니다 :)

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