58
votes
How to set the preferred network interface in Linux
Here's the complete answer, in case it helps others:
To make packets with destinations 192.168.10.* use eth0, and all other packets use eth1:
1) View your current routing table
ip route list
One ...
- 761
47
votes
Accepted
What makes a private IP address not routable?
Private IP addresses are routable, albeit they are not publicly routed. Basically, a router will route a private address to private/internal LAN, rather than to the internet.
To expand my answer: a ...
- 50.6k
36
votes
Multiple devices with one IPv6 to the Internet?
IPv6 is designed to not do that. Trying IPv4 style NAT with IPv6 will break things. That said, I'm pretty sure you can do NAT IPv6 with Linux iptables, so it's not impossible. But I would strongly ...
- 7,982
34
votes
Why "Nexthop has invalid gateway" when it seems to be defined?
Perhaps something like:
ip route add <gateway IP> dev <interface on which it should be reachable>
and then
ip route add default via <gateway ip>
"Direct connection" can ...
- 449
30
votes
Accepted
Are people really going to use public IPv6 addresses on their private networks?
Is that how IPv6 is intended to work?
In short, yes. One of the primary reasons for increasing the address space so drastically with IPv6 is to get rid of band-aid technologies like NAT and make ...
- 16.9k
29
votes
Adding a route to specific host go out a specific interface
On a newer machine using the ip binary the syntax to add a route is slightly different (but thankfully really consistent for hosts/networks/etc).
ip route add 10.0.1.3 via 10.0.0.1 dev eth0
If you ...
- 846
22
votes
How to verify a AWS VPC (S3) endpoint works?
I guess the straightfwd way is to actually probe those routes.
You can traceroute to s3 and see if the NAT Gateway's internal IP is anywhere in the output (eg. the first hop).
First, check the NAT ...
- 320
21
votes
Are people really going to use public IPv6 addresses on their private networks?
We use public IPv6 addresses in our company network for all devices.
We use a stateful firewall on our gateway, that:
allows all icmpv6
allows new connections from internal network out
allows ...
- 1,583
21
votes
Multiple devices with one IPv6 to the Internet?
IPv6 doesn't have a NAT standard the way IPv4 does. There is an EXPERIMENMTAL RFC for one-to-one NAT (one outside address for each inside address) on IPv6, but explicitly forbids what you want to do (...
- 3,273
20
votes
OpenVPN - how to stop public traffic routing through vpn server?
The problem was caused by Network Manager which was handling the opvn config. To disable sending all traffic through the VPN do this
Click NetworkManager applet icon > VPN Connections > Configure VPN....
- 533
19
votes
Can switches do VLAN routing?
L2 switches cannot do Inter-VLAN routing, since they only take care of L2 network stuff, that is, forward frames between links. If it is a L3 switch, then it can do IP protocol routing between VLANs.
- 37.6k
19
votes
Accepted
IP Routing - For Office Move
When a host tries to access another host in the same subnet, it issues an ARP request for the host MAC address. If no ARP reply is received, then the host is declared unreachable.
So, therefore you ...
- 37.6k
18
votes
Difference beetween DNAT and REDIRECT in IPTABLES
REDIRECT does alter the destination IP address to send to the machine itself as answered by Warner@. But I'd say that answer is not totally correct, or a bit misleading.
REDIRECT is not just for ...
- 181
18
votes
Accepted
Disabling rp_filter on one interface
Info there: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/tree/Documentation/networking/ip-sysctl.txt?h=v4.9#n1090
Note the last sentence that would explain your attempts:
...
- 12.8k
17
votes
Accepted
Use ip route add to add multicast routes to multiple interfaces
That you have multicast going through your Linux box by using unicast routing is a combination of a couple of lucky circumstances.
Multicast routing is not the same as unicast routing. Unicast ...
- 3,273
15
votes
Accepted
How to verify a AWS VPC (S3) endpoint works?
I have found a method to verify the VPC endpoint usage.
Log in to an AWS EC2 instance in the VPC
Configure the aws cli client
run aws ec2 describe-prefix-lists; for Windows PowerShell, Get-...
- 2,084
14
votes
Are people really going to use public IPv6 addresses on their private networks?
If there is no need for outside connectivity, then private networks can be used. That is the reason for defining private address space also in IPv6.
NAT is a hack that was invented to delay IPv4 ...
- 37.6k
14
votes
Why "Nexthop has invalid gateway" when it seems to be defined?
A gateway address can only be on a directly connected network. The 10.7.0.0/24 network is not directly connected to your host 10.0.0.2, but is instead separated by another network, which is connected ...
- 248k
13
votes
How to Set Up Linux Server As A Router with NAT
I think the other answers missed some important points. Here's another way, assuming iptables is in a fresh state, once again using eth0 as the internal interface and eth1 as external:
Enable IP ...
- 317
13
votes
Why "Nexthop has invalid gateway" when it seems to be defined?
I've also encountered the problem, you need
ip link set LINK_NAME up
be aware that if the link has dependencies on other links, such as veth pair, you also need enable them too.
- 395
12
votes
Accepted
Set up public ip on server
Presenting a service to the Internet definitely should not be done unless you know what you're doing. Fortunately it's mostly a matter of not being naïve, but you definitely should have passed a ...
- 5,099
11
votes
Accepted
Changing OpenVPN DHCP pool
OK finally it is solved with some changes on the config file:
port 1194
proto udp
dev tun
ca /etc/openvpn/ca.crt
cert /etc/openvpn/server.crt
key /etc/openvpn/server.key
dh /etc/openvpn/dh2048.pem
...
- 279
11
votes
Is it possible to override a single domain name using dnsmasq?
Add this line to /etc/dnsmasq.conf:
addn-hosts=/etc/dnsmasq.hosts
Then insert your domain names into /etc/dnsmasq.hosts:
10.0.0.1 prod.example.com.
10.0.0.2 dev.example.com.
Don't forget the ...
- 290
11
votes
Accepted
AWS EC2 SSH from my IP address which has changed
Go with #3. It's trivial to write a small script you can run that will:
Fetch your current public IP
Use that IP and awscli to update your security group
Stick this script on your desktop and you're ...
- 110k
11
votes
How to verify a AWS VPC (S3) endpoint works?
You can turn on S3 logging and check if the files are being accessed from your private IP rather than public. If your logging shows private IPs are accessing the buckets you've configured it correctly....
- 111
11
votes
Can switches do VLAN routing?
VLANs are used to create different subnets which means different broadcast domains. You need to have either a router or a Layer-3 switch in order to forward traffic between different VLANs (different ...
- 36.9k
11
votes
What makes a private IP address not routable?
Private IP addresses (as per RFC 1918) are very much routable, just not on the public Internet.
Usually, private IP addresses are filtered by the ISP. Your access router should also be configured to ...
- 11.7k
10
votes
Accepted
OpenBSD: Gateway outside subnet (works in Linux)
This is an old thread, but here goes.
As it happens, I run a number of OpenBSD VMs on an ESXi 6.0 running at SoYouStart, a daughter company of OVH. The network setup there is the same as with OVH ...
- 228
10
votes
How to enable traceroute in linux machine
We can see from man 8 traceroute that:
UDP is the default traceroute mechanism on Linux
traceroute expects to get an "ICMP unreachable" message in response to its query
traces start at port 33434 and ...
- 964
10
votes
Can switches do VLAN routing?
Routing is a layer 3 function, while VLAN only concern Layer 2.
When a computer A want to send data to another host B, using the IP protocol it will first check if B is in the same network as himself ...
- 2,028
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