[Cisco] Router 與 Layer 3 Switch 簡易比較

Layer 3 Switch 彌補Router 不足之處

用在Lan的範圍內與Router互補

Inter  -  vlan Routing

 簡易比較

	Router	Layer 3 Switch
CPU 、RAM	勝	輸
Routing 功能	有	有
Wire-speed 加速	X	V
路由表大小	多	少
NAT	有	無
協定支援度	高	低
WAN 、QOS	有	無

指令:

1.no switchport
2.ip routing

[Cisco] RIP、EIGRP、OSPF簡易比較

RIP 、EIGRP、OSPF 差別小筆記

	RIPv2	EIGRP	OSPF
DV / LS ?	distance vector	distance vector	link state
成本	Hops (最大15)	BW + Delay	Cost  (REF/BW)
Auto Summary	V	V	X
Manual Summary	Any router	Any router	ABR(ASBR)
防止路由迴圈	X	V	V
CIDR	Classful only	Classful [wildcard]	Wildcard only
Neighbor	X	V	V
演算法		DUAL	Dijkstra's SPF

更詳細可以參考:
https://learningnetwork.cisco.com/thread/63810

EIGRP

1. Hybrid protocol –

     Distance vector (first time) Link state (updates)

2. Summarization possible on all the routers.

3. Easy to configure (No area configs) & can separate

     routes wrt to AS numbers
4. Not much processor oriented as the metric from the neighbor is believed and also feasible successor in place

5. No dependency… like underlying area 0

6. Add as many routers u want, with proper planning

     and summarization.

7. Easy to design and redesign

8. Only 2 route types (Internal & external)

9. Convergence is faster as the hello:dead = 5:15 & also

     because of the successor & feasible successor.

10. Supports only md5 authentication

11. Hello/Dead shud not match, helps while making

       changes

12. Stuck in Active scenario (can be addressed with

        summarization / stub / disabling active-timers)

13. In modern DMVPN designs, EIGRP has managed to

        move past 3500 peers

14.  Equal cost load-balancing is possible ! (variance)

15. traffic-share balanced: traffic load balancing

       according to the cost of the available links.

OSPF

1. Purely a Link state protocol.

2. Summarization possible on ABR & ASBR only.

3. A bit complex to design wrt to areas, as all the OSPF

      routes gets traverse across OSPF domain.

4. Consumes more resources of the device to run SPF

     every time a change happens in network.

5. Must have to rely on area 0 to communicate

      interarea.

6. Adding routers in an area may increase the size of

     LSBD

7. May be easy to desing, but for redesigning and

     adding areas, virtual link is required.

8. 11 types of routes (LSAs)

9. Conversion time is higher than EIGRP,

      hello:dead=10:40

10. Supports clear text & md5 authentication

11. Hello/dead timers shud be the same, bit difficult to

       make the changes

12. No Stuck in active.

13. Equal cost load-balancing is not possible !

[Cisco] Load balancing 與 Load sharing 比較

常常聽到對於Server或網路規劃的負載平衡有些奇怪的誤解
尤其是 Load balancing 與 Load sharing 常常隨便混用著說

剛好CISCO 論壇有人有類似的疑問 我覺得回答的還蠻清楚的
( learningnetwork.cisco.com/thread/63821 )

In short, load balancing tries to distribute traffic evenly over multiple paths, whereas, load sharing intends to do it (for the lack of a better term) equally. True load balancing is difficult to achieve. For example, let's say there were two links (100 mbps and 300 mpbs) and a router needed to send out 600 mbps of traffic. Load balancing would distribute the traffic evenly, sending 300 mbps on each link. On the contrary, load sharing would divide the traffic equally based on the available resources, sending 200 mbps on the slower link and 400 mbps on the faster one.

簡而言之，負載平衡嘗試在多個路徑上均勻地分配流量，
而負載分配打算同等執行（缺少更好的說法）。真正的負載平衡很難實現。
假設有兩個連結(路徑 : 100 mbps 和 300 mpbs)和一個需要發送600 mbps流量的Router。
預設情況下 負載平衡將均勻分配流量，每條連結發送300 mbps。
相反，負載共享(Sharing)會根據可用資源平均分配流量，
在較慢的連結上發送200 mbps，在較慢的連結上發送400 mbps。

永久連結

Load sharing  能將流量控制平均在這兩條線路上,
而load balance 則不僅僅能分送,能考慮到兩條線路頻寬的不同而予以不同分擔(可能需要手動設定)

Load Balancing 也可依等比例作分配常見的Ether Channel (=Port Channel)就是Load balancing EIGRP 動態路由的 variance做 load balancing來說可以手動設定依照 Metric(可以說是路由成本) 的反比例分配流量

技術點來解釋:

Many Network administrators at times get tangled in the conceptual difference of Load Balancing and Load Sharing. Prima facie, both may be thought of as one of the same thing, however as we drill down, the terms tend to differ. So let’s differentiate how both Load Balancing and Load Sharing concepts differ from each other and where are they used.

Load balancing is more of dynamic technique of distributing the load across 2 or more links while Load Sharing works by statically splitting the traffic types and then distributing the load across multiple links. Though we understand that dynamic load distribution will be more efficient on equal load distribution. While Load Balancing utilises round robin or maximum connections etc. to distribute traffic, Load sharing 1st splits the traffic based on source or destination IP/Mac address etc. and then distributes traffic across links.


許多網管有時會搞混負載平衡和負載分享的概念差異。乍看之下兩者都可以被認為是同一件事，但是當我們深入研究時，其實有所不同。
負載平衡(balancing)更多是透過兩個或多個連結分配負載的動態技術，
而負載分配(sharing)通過靜態拆分流量類型然後跨多個連結分配負載來工作。
雖然我們知道動態負載分配在等負載分配上會更有效。

雖然負載平衡利用循環或最大連接等來分配流量，
但負載分配會根據源或目標IP / Mac地址等拆分流量，然後跨連結分配流量。 

Below table gives simple comparison of both the concepts – Load Balancing vs Load Sharing

(https://ipwithease.com/load-balancing-vs-load-sharing/)

[Cisco] 架設 DHCP Server 派發IP至不同網段PC

準備環境:

Packet Tracer 7.1

解說 :

1.中間的Router 0 直連了三個不同的網段 :
192.168.0.0/24   、 192.168.1.0/24 、192.168.10.0/24(VLAN 10 )、192.168.20.0/24(VLAN 20)

遠方的網段:10.0.99.0/24 、10.0.0.0/24、10.0.0.1/24


2.將R0建立DHCP伺服器 分別派發至每個網段的PC使其可以Ping到Router 0

提示: 非直連網段必須使用DHCP Relay、不同網段的Router需要認識彼此。

3. R0為中心左方(G0/2)只能Ping到R0、右方只能Ping到R0(G0/0)、下方只能Ping 到R0(G0/1)

--------------------------

前置作業:
在每個介面上no shut 並Key上IP

DHCP指令:

設定 DPHCP SERVER給下方192.168.1.0/24 PC
##ip dhcp pool DHCPNAME    " DHCPNAME"自行命名,命名清單時大寫為佳##
Global模式下:
ip dhcp pool IT0
network 192.168.0.0 255.255.255.0

default-router 192.168.0.254     #該網段的Gateway  ,意思是封包要出去的interface
##dns-sever 100.100.100.1## (模擬器上可打可不打)
exit

查看DHCP分配:

en
 show ip dhcp binding



待續