r****o 发帖数: 1950 | 1 这是我面试时碰到的一道题目,答得不好。希望版上的高人能够解答一下。 |
s*****g 发帖数: 1055 | 2 In the old days when switch and routers are totally two entities, you need
to put a router on-stick of a switch to achieve inter-VLAN communication, so
combining the two to one saves one box. Nowadays any vendor can do routing/
switching in one box, this gives network designer more flexibility,same box
can be configured as access, aggregation and core layer of the network.
What else? |
s*****g 发帖数: 1055 | 3 A better interview question for router/switch is:
How does the router/switch know when to route a packet and when to switch a
packet? |
r****o 发帖数: 1950 | 4 是不是可以先查这个packet的IP地址,如果是在同一个网络里面,就用switch,否则就
route?
a
【在 s*****g 的大作中提到】 : A better interview question for router/switch is: : How does the router/switch know when to route a packet and when to switch a : packet?
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s*****g 发帖数: 1055 | 5 nope, nice try. You are answering theory, I was asking operation. |
c*****i 发帖数: 631 | 6 switch的每个vlan有个virtual interface相当于网关,switch根据mac address
switch,virtual interface收到后在做routing。
【在 r****o 的大作中提到】 : 是不是可以先查这个packet的IP地址,如果是在同一个网络里面,就用switch,否则就 : route? : : a
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w***s 发帖数: 321 | 7 我一般倾向不将switching和bridging等同起来. 剩下的取决于dmac
【在 s*****g 的大作中提到】 : A better interview question for router/switch is: : How does the router/switch know when to route a packet and when to switch a : packet?
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r****o 发帖数: 1950 | 8 操作细节不清楚,谁能说一下?
【在 s*****g 的大作中提到】 : nope, nice try. You are answering theory, I was asking operation.
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j*a 发帖数: 14423 | 9 check dst mac.
if dst mac belongs to switch then route, otherwise switch.
【在 s*****g 的大作中提到】 : nope, nice try. You are answering theory, I was asking operation.
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s*******a 发帖数: 42 | 10 感觉说反了?
【在 j*a 的大作中提到】 : check dst mac. : if dst mac belongs to switch then route, otherwise switch.
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e**********w 发帖数: 117 | 11 没反
joa说的是正解
【在 s*******a 的大作中提到】 : 感觉说反了?
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t*******r 发帖数: 3271 | 12 Good for design, but when it comes to the greater detail of internal
architecture of the network equipment, scaling has always become an issue.
You can't turn on everything and expect huge scaling number for all the features,
you've got tradeoffs everywhere.
Router with L2 forwarding: Juniper MX series / ALU SR series
Switch with L3 routing: Cisco 7600 series
All depend on the internal processing of frames and packets.
MX is the one I know best so let me try:
Ichip is primarily used for L3 packe |
r****o 发帖数: 1950 | 13 为什么呢?能不能解释一下?
【在 e**********w 的大作中提到】 : 没反 : joa说的是正解
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r****o 发帖数: 1950 | 14 等了一天,没人回答。 :(
【在 r****o 的大作中提到】 : 为什么呢?能不能解释一下?
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r****o 发帖数: 1950 | 15 我怎么也觉得说反了。有谁能解释一下joa的意思吗?
【在 e**********w 的大作中提到】 : 没反 : joa说的是正解
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t*******r 发帖数: 3271 | 16 规定而已~ 有啥好解释的
【在 r****o 的大作中提到】 : 我怎么也觉得说反了。有谁能解释一下joa的意思吗?
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L******t 发帖数: 1985 | 17 Right, but only for unicast.
For multicast, switching & routing happen simultaneously.
【在 e**********w 的大作中提到】 : 没反 : joa说的是正解
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m********d 发帖数: 188 | 18 good question: asking operation, not theory.
from operation stand of point, when a L2/3 device receives a packet ( or
frame ), first thing it looks at is MAC. if it's intra-vlan traffic, it's in
MAC table for that VLAN, if inter-VLAN traffic, MAC is SVI's MAC. so far,
L2 engine is processing the packet. now L3 engine kicks in, of course, for
inter-VLAN traffic. L3 engine will look at IP address, then make forwording
decision, of course again, it's hardware processed, centralized/distributed
, e |
s*********4 发帖数: 1980 | 19 简单说,应该是速度和效率吧.参考CISCO的multilayer switching with Content
Express Forwarding (CEF)可以展开来回答这个问题.用于layer 2 switching的
Forward Information Base table建立于layer 3的routing table基础上.Layer 2处理
不了的某些类packets可以立刻转给Layer 3的Engine处理等等.
【在 r****o 的大作中提到】 : 这是我面试时碰到的一道题目,答得不好。希望版上的高人能够解答一下。
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z**r 发帖数: 17771 | 20 CEF怎么成了content express forwarding了
【在 s*********4 的大作中提到】 : 简单说,应该是速度和效率吧.参考CISCO的multilayer switching with Content : Express Forwarding (CEF)可以展开来回答这个问题.用于layer 2 switching的 : Forward Information Base table建立于layer 3的routing table基础上.Layer 2处理 : 不了的某些类packets可以立刻转给Layer 3的Engine处理等等.
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s******v 发帖数: 4495 | 21 而且layer 2怎么会有fib? cef,还是读ingress packet dst ip,和layer 2也没关系
啊。
【在 s*********4 的大作中提到】 : 简单说,应该是速度和效率吧.参考CISCO的multilayer switching with Content : Express Forwarding (CEF)可以展开来回答这个问题.用于layer 2 switching的 : Forward Information Base table建立于layer 3的routing table基础上.Layer 2处理 : 不了的某些类packets可以立刻转给Layer 3的Engine处理等等.
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s******v 发帖数: 4495 | 22 还有一个好处
even for the inter-vlan traffic desitinated to the same switch,they have to
travel around from switch to router, back to switch.
so
routing/
box
【在 s*****g 的大作中提到】 : In the old days when switch and routers are totally two entities, you need : to put a router on-stick of a switch to achieve inter-VLAN communication, so : combining the two to one saves one box. Nowadays any vendor can do routing/ : switching in one box, this gives network designer more flexibility,same box : can be configured as access, aggregation and core layer of the network. : What else?
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s*********4 发帖数: 1980 | 23 嗯,错了,是Cisco Express Forwarding, 还有layer 3 ,not layer 2.这砖一下就把玉
都给引出来了.
【在 z**r 的大作中提到】 : CEF怎么成了content express forwarding了
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n********x 发帖数: 5 | 24 我觉得最大的好处就是便宜.
有些小公司一共就几台电脑,买个switch太贵,只买个router口又不够,而且设备多了管
理也麻烦.
于是就出现了router和switch整合的产品,因为有需求.
比如做ISP的就根本不会需要用到switch的L3的功能. |
t*******r 发帖数: 3271 | 25 yup, physical port fan-out.
【在 n********x 的大作中提到】 : 我觉得最大的好处就是便宜. : 有些小公司一共就几台电脑,买个switch太贵,只买个router口又不够,而且设备多了管 : 理也麻烦. : 于是就出现了router和switch整合的产品,因为有需求. : 比如做ISP的就根本不会需要用到switch的L3的功能.
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