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15

A single anycast IP address does not give you the same redundancy as two unicast IP addresses in distinct IP prefixes would. Often the hardest problem for redundancy is not when something fails completely, but rather when it is misbehaving just enough to still pass the health checks, but not actually be functional. I have seen an anycast DNS setup where a ...


8

Blocking outbound connections to destination TCP port 25 is something that a lot of ISPs do today. While I don't particularly like it, it's a pretty typical thing that gets done. So long as you publish to your users that you're making this change, and perhaps take some packet captures to pre-emptively see who might be effected by the change, I think it's ...


8

Without further details it's difficult to give an appropriate answer. In the simplest case, with everything on the same IP subnet (including router2's clients), same VLAN, dynamic IP attribution, etc., i.e. the routers can communicate directly without any special switching/routing configuration, all you need is cabling and: set router1 as default gateway ...


7

The routes metric is to set preference among routes with equal specificity. That is true of routing in general (i.e. Cisco, Windows, etc). So the model works like: Find the most specific route (aka the longest prefix match*) If there are multiple routes with the same specificity, pick the one with the lowest administrative distance (This distinguishes ...


6

No, you can't do that on the host directly. You need a VM to handle the routing. ESX is not a router.


5

You want network address translation (NAT) for your LAN: source NAT for your clients, destination NAT for your servers. Your LAN firewall probably provides this capability. Then, you need to configure your firewall to forward ports 80 and/or 443 from the external IP address to your server's LAN IP address.


5

The stacking protocol should handle loop detection and prevention. It may be using spanning tree, it may be doing something else. You best bet is to read the docs on how Dell's stacking works. I'm not primarily a network guy, and my beginner-level.. For the love of god if you don't know what you are doing don't turn off spanning tree. There are a few ...


5

Nah you can't, there's nothing to refer to anyway (e.g. logical ID). Just create your own main table ;-). This is probably one of the reason it can't be used: One way to protect your VPC is to leave the main route table in its original default state (with only the local route), and explicitly associate each new subnet you create with one of the custom ...


5

Short answer: No Longer answer: A router which implements just the router functionality does not and cannot verify UDP and TCP checksums. However routers do exist with additional functionality. If the router has NAT and/or firewall functionality, the answer may differ. There are many reasons for a router not to verify the checksums: It would slow down ...


4

Create a file in /etc/syconfig/network-scripts/route-eth0 add add the following 192.168.20.0/24 via 192.168.20.253 dev eth0 I have always used this approach. I have found this to be the best approach. FYI: Check -- https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/s1-networkscripts-static-routes.html


4

You can absolutely use a DHCP server to serve a scope it's not a part of, so long as the traffic can flow between the two subnets. The trick is that DHCP requests are generally only served out to the broadcast domain the client is on, to so get around that, you place an IP-helper address on the piece of network gear the client is connecting through so that ...


4

First off, the cables on the stacking module (if stacking is configured correctly) wouldn't be a loop on your network. These are part of the Stacking Module which is/should be separate from your standard TCP/IP network. It may still be that the stack is misconfigured but that is not part of the question so we'll move on. STP or any variant of STP (MSTP, ...


4

Best practice is to use at least two addresses from different prefixes and giving them a name under two different TLDs. Both those addresses can be anycast if you want. Having only one IP address will give you a single point of failure. If the routing to that address doesn't work (configuration error, an anycast instance not working correctly, the prefix ...


4

There is a simple fix for this, at least when it comes to the most popular Cisco routers: mls cef maximum-routes ip 768 This requires a reboot. Also see Cisco's documentation about adjusting the TCAM to allocate more IPv4 space (and less IPv6): ...


4

What you are describing is what happens when a switch's CAM table is full, where it can no longer learn MAC address and it forwards packets out every port. It might be hard to figure out if this is the problem with an unmanaged switch, but with a managed switch you should be able to display the CAM table. What also would help in this question is a diagram ...


4

First of all: the iptables -A command add the new rule after the end of your actual chains. They were processed only after the last rule in your chains. But it won't happen, because the last rule already filters everything out! You need to put these commands before your last rule, which can be done with the -I <n> flag of the iptables. Second: ...


4

You want policy-based routing. Quick distro-agnostic example: echo 200 custom >> /etc/iproute2/rt_tables ip rule add from 192.168.1.8 lookup custom ip route add default via 10.76.8.50 dev eth0 table custom


4

VLANs have nothing to do with your IP addressing scheme. You're conflating layer 2 and layer 3. At the risk of shamelessly plugging myself I'll suggest you have a look at "How do VLANs work?" and "Best way to segment traffic, Vlan or subnet" (and maybe also "Network: Many subnets in 1 VLAN =? possible"). As a "quick fix": Assuming you're using ...


4

In RedHat Entrprise Linux 7.0 (the "upstream" of CentOS 7.0) the intended interaction with iptables is through firewalld. Manually modifying the iptables configuration, while possible, is not the intended method if interaction. If you do want to modify the iptables configuration directly you might want to have a look at documentation about iptables. You're ...


3

Anycast is not a widely accepted type of communication in IPv4, but it is present in IPv6. Three type of communication in IPv4 are 1) Unicast, 2) Multicast 3) Broadcast. 1) IPv4 Unicast One-to-One type of communication. A network device communicates with another network device. Layer 3 address used for Unicast is IPv4 Class A, Class B, Class C addresses. ...


3

Due to the fact that both links have the same IP gateway, you must set in some way the interface you want to use in your routing tables. The syntax is the following: gateway=[ip]%[interface] + specific preferred source; given this fact, in your router these routes should look like the following: /ip route gateway=109.60.164.1%gateway1 pref-src ...


3

The Google term you're looking for is "Looking Glass". Try Hurricane Electric's, at http://lg.he.net/, to get an idea.


3

You should convert your Wireless routers to Wireless Access points. Use the LAN Port of the device Disable DHCP (Server) Disable NAT This should "downgrade" the device to a standard Access point, and you should be good.


3

10.8.2.12 sees 10.8.2.254 as being on the same subnet, therefore it's requesting the MAC address of 10.8.2.254 to insert it as a dest MAC in future packets to 10.8.2.254. Since 10.8.2.254 doesn't exist, no one is replying and 10.8.2.12 never finds out what MAC to set as the dest MAC. Try using proxy_arp on your main server. echo 1 > ...


3

The RFC 1034 only states that you require two DNS servers. This isn't a mandatory requirement, but a recommendation, so do with it what you will. Regardless, if you want HA, your 2 DNS servers can be assigned the same IP using anycast, and the only thing your end users would notice when one DNS server fails, is a momentary lack of connectivity as the network ...


3

If you look at the iproute2 gitweb, you'll see it's showing the status of the RTN_ANYCAST bit set on the kernel routing structure. If you cross-reference that with the kernel source (rtnetlink.h) you'll see the following comment: RTN_ANYCAST, /* Accept locally as broadcast, but send as unicast */ If you check ...


3

Add the following to your command: route -p add 46.137.226.16 mask 255.255.255.255 10.20.1.1 METRIC 1 IF ## Where ## is the relevant interface number from the top of "Route Print" : Assigning a metric 1 ensures that this will should always be the default route for this IP.


3

SOLVED IT!! My drive was mapped with "\computername\share" which means that it will look for "computername" in the default gateway's subnet, right? When i mapped the drive with "\172.x.x.x\share" it worked! Of course without default gateway and the static route "route add 172.0.0.0 mask 255.0.0.0 172.21.61.161 metric 1 if 11" I can't belive that i missed ...


3

Thanks for all the inputs. I came up with a shell script to do the job for me. I believe this would be helpful for other users also to perform the task. Please note that the local machine IP. Please do the necessary changes accordingly. #!/bin/sh echo "Enabling Traceroute..." #Outbound UDP traffic Policy iptables -I OUTPUT -o eth0 -p udp --dport ...


3

Ok, this can be done, but it's definitely not as easy as it could (and should) be. Basically, the trick is using Azure's "local networks" to configure Azure gateways as we want, even if we can't directly touch their configuration. In order to set up a connection between two Azure virtual networks, you need to define two matching "local networks", and then ...



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