windows xp系统如果有多个网卡，那么两个网卡可以做router的功能，也可以做bridge的功能。
当做router功能时，两个网卡地址不能是同一个subnet。
当做bridge功能是，两个网卡只有一个地址，另外一个网卡连接的网段，自动同步为同一网段。
这样有一个优势，就是特定设备需要扩展网络连接的时候，不用另外接hub或者switch，xp双网卡就可以解决。
具体操作步骤是在网络配置中，同时选择2个网卡，然后右键，出现的菜单有bridge这项，选择就可以了。
Thursday, July 31, 2008
交换机光纤连接问题
在现场连接中，由4506--4506--3550的拓扑。
4506--3550连接不正确，后来发现是因为gbic卡不匹配。3550上的gbic卡是ws-g5484，是一个多模光纤转换器。CISCO 1000BASE-SX GBIC
The Cisco 1000BASE-SX GBIC (WS-G5484) operates on ordinary multimode fiber (MMF) optic link spans up to 1815 feet (550 m) long.
4506上插的是ws-g5486，是单模多模兼容的。CISCO 1000BASE-LX/LH GBIC
The Cisco 1000BASE-LX/LH GBIC (WS-G5486) fully complies with the IEEE 802.3z 1000BASE-LX standard. However, its higher optical quality allows it to reach 6.2 miles (10 kilometers) over single-mode fiber (SMF), compared with the 3.1 miles (5 km) specified in the standard. 卡上写的是ws-g5486lx，但是路由器识别是1000base LH.
两个gbic不匹配的地方是光波波长不一样，所以无法通信。sx是多模传输距离是550米，lx的多模是550米，单模是10km。lx的优势是，既可以使用MMF，也可以使用SMF。
如果用肉眼识别，Sx卡启动后，不插光纤，可以看到右边端口发光（右边端口是发射）。LX卡启动后，看不到端口发光。
两个4506连接的问题是，端口被shutdown。line card用的是WS-X4306-GB，有6个gbic端口。指示灯在端口下方，当端口shutdown后，会显示黄光，如果no shutdown，不亮灯。如果连接正常，则显示绿光。有一个端口插上gbic，显示non support gbic，应该是端口fail。还有一个端口显示nonconnected，但是光纤已经连接。热插拔换一个端口就好。
经验总结：1 检查gbic的类型
2 如果端口不行，热插拔换到另外的端口试试。
3 也可以换一个gbic卡试试
4506--3550连接不正确，后来发现是因为gbic卡不匹配。3550上的gbic卡是ws-g5484，是一个多模光纤转换器。CISCO 1000BASE-SX GBIC
The Cisco 1000BASE-SX GBIC (WS-G5484) operates on ordinary multimode fiber (MMF) optic link spans up to 1815 feet (550 m) long.
4506上插的是ws-g5486，是单模多模兼容的。CISCO 1000BASE-LX/LH GBIC
The Cisco 1000BASE-LX/LH GBIC (WS-G5486) fully complies with the IEEE 802.3z 1000BASE-LX standard. However, its higher optical quality allows it to reach 6.2 miles (10 kilometers) over single-mode fiber (SMF), compared with the 3.1 miles (5 km) specified in the standard. 卡上写的是ws-g5486lx，但是路由器识别是1000base LH.
两个gbic不匹配的地方是光波波长不一样，所以无法通信。sx是多模传输距离是550米，lx的多模是550米，单模是10km。lx的优势是，既可以使用MMF，也可以使用SMF。
如果用肉眼识别，Sx卡启动后，不插光纤，可以看到右边端口发光（右边端口是发射）。LX卡启动后，看不到端口发光。
两个4506连接的问题是，端口被shutdown。line card用的是WS-X4306-GB，有6个gbic端口。指示灯在端口下方，当端口shutdown后，会显示黄光，如果no shutdown，不亮灯。如果连接正常，则显示绿光。有一个端口插上gbic，显示non support gbic，应该是端口fail。还有一个端口显示nonconnected，但是光纤已经连接。热插拔换一个端口就好。
经验总结：1 检查gbic的类型
2 如果端口不行，热插拔换到另外的端口试试。
3 也可以换一个gbic卡试试
Wednesday, July 9, 2008
Proxy ARP on Windows XP
The Proxy ARP rules of Windows XP.
在windows系统中有如下结论：
总结：
主机不设默认网关－－－－从不向本网段外的地址arp请求，不会发生代理arp
主机设本网段其他地址为网关－－－－－－如果目的是非本网段地址，则向所设 的网关arp请求不会发生代理arp
主机将网关设为非本网段地址－－－－－－－－向外网发包时，会arp请求所设网关的mac，如果此时真网关开启代理arp，代理就会发生
主机将网关设为自己－－－－－－－－可以对任何地址（你的目的地址，不管是多少）发arp请求，如果真网关开启代理arp，代理就会发生。
1. If the default gateway is not set, XP will not send arp request, So Proxy ARP will not work
2. If the default gateway is in the same subnet. XP will only not send arp request, all the IP is sent to the dafault gateway MAC address. If the default gateway is not working, the other Proxy ARP will not working either.
3. If the default gateway is in different subnet, the Proxy ARP will work!
4. If the default gateway is the set the itself, the Proxy ARP will work!
In conclution, to make proxy arp work for xp, the default gateway must set and must set to itself or different subnet ip address. The best is to set the same ip for default gateway.
The test is done and proved on July 09, 2008. The workstation is windows XP, and the network is Cisco 3560 and 6509.
在windows系统中有如下结论：
总结：
主机不设默认网关－－－－从不向本网段外的地址arp请求，不会发生代理arp
主机设本网段其他地址为网关－－－－－－如果目的是非本网段地址，则向所设 的网关arp请求不会发生代理arp
主机将网关设为非本网段地址－－－－－－－－向外网发包时，会arp请求所设网关的mac，如果此时真网关开启代理arp，代理就会发生
主机将网关设为自己－－－－－－－－可以对任何地址（你的目的地址，不管是多少）发arp请求，如果真网关开启代理arp，代理就会发生。
1. If the default gateway is not set, XP will not send arp request, So Proxy ARP will not work
2. If the default gateway is in the same subnet. XP will only not send arp request, all the IP is sent to the dafault gateway MAC address. If the default gateway is not working, the other Proxy ARP will not working either.
3. If the default gateway is in different subnet, the Proxy ARP will work!
4. If the default gateway is the set the itself, the Proxy ARP will work!
In conclution, to make proxy arp work for xp, the default gateway must set and must set to itself or different subnet ip address. The best is to set the same ip for default gateway.
The test is done and proved on July 09, 2008. The workstation is windows XP, and the network is Cisco 3560 and 6509.
Second IP Address Makes the Problem
There is a network issue happened in my company.
One server is relocated and the administrator wanted to keep the old ip address which is 10.200.200.5. So I created a vlan 200 and assinged IP address 10.200.200.0/24. The Vlan interface ip is 10.200.200.1.
After the configuration, we server can ping all other vlans except 10.0.99.5. I have checked the ACL on all devices and found no ban. I pinged from the switch and found that: 10.0.99.5--10.200.200.1 is OK, 10.200.200.5--10.0.99.1 NOT OK.
So the problem is on the server. After login to the server, I found that the is a secondary ip address on the server's NIC. The secondary ip address is 10.0.99.9/24. After removing the secondary ip address, the communication is GOOD.
The issue is when the server sends packet to 10.0.99.0/24, the MAC address is not pointing to ther gateway. And there is no Proxy ARP on the default gateway. So the server cannot get the MAC address of any ip address of 10.0.99.0/24. This makes the problem.
In conclusion, the problem is related to ARP. The server cannot get the mac of ip.
One server is relocated and the administrator wanted to keep the old ip address which is 10.200.200.5. So I created a vlan 200 and assinged IP address 10.200.200.0/24. The Vlan interface ip is 10.200.200.1.
After the configuration, we server can ping all other vlans except 10.0.99.5. I have checked the ACL on all devices and found no ban. I pinged from the switch and found that: 10.0.99.5--10.200.200.1 is OK, 10.200.200.5--10.0.99.1 NOT OK.
So the problem is on the server. After login to the server, I found that the is a secondary ip address on the server's NIC. The secondary ip address is 10.0.99.9/24. After removing the secondary ip address, the communication is GOOD.
The issue is when the server sends packet to 10.0.99.0/24, the MAC address is not pointing to ther gateway. And there is no Proxy ARP on the default gateway. So the server cannot get the MAC address of any ip address of 10.0.99.0/24. This makes the problem.
In conclusion, the problem is related to ARP. The server cannot get the mac of ip.
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