Public Subnet re-assignments
First, sorry if this is a bit of a noob question. I'm trying to find a way of preventing a slew of traffic to an IP, or IP's, when I join two /30 public subnets to a /29. It appears that while the ranges are /30 someone is trying to brute-force the network and/or broadcast addresses for the ranges. When I change them to be a /29, now the router sees the traffic and starts dropping packets. Are there any suggestions for mitigating this behavior or is it just the nature of the beast? -- 101010
You’re using just the two middle IPs in the four that make up the /30 set, right? IOW, the subnet x.x.x.0/30 should have .0 and .3 unused (they’re broadcast), and you use .1 and .2. -mel
On Jun 25, 2019, at 9:41 AM, Scott <scott@viviotech.net> wrote:
First, sorry if this is a bit of a noob question.
I'm trying to find a way of preventing a slew of traffic to an IP, or IP's, when I join two /30 public subnets to a /29. It appears that while the ranges are /30 someone is trying to brute-force the network and/or broadcast addresses for the ranges. When I change them to be a /29, now the router sees the traffic and starts dropping packets. Are there any suggestions for mitigating this behavior or is it just the nature of the beast?
-- 101010
Also, what do you mean by “join to /30 public subnets to a /29”? You can’t overlap subnets, if that’s what you’re thinking. -mel
On Jun 25, 2019, at 3:27 PM, Mel Beckman <mel@beckman.org> wrote:
You’re using just the two middle IPs in the four that make up the /30 set, right? IOW, the subnet x.x.x.0/30 should have .0 and .3 unused (they’re broadcast), and you use .1 and .2.
-mel
On Jun 25, 2019, at 9:41 AM, Scott <scott@viviotech.net> wrote:
First, sorry if this is a bit of a noob question.
I'm trying to find a way of preventing a slew of traffic to an IP, or IP's, when I join two /30 public subnets to a /29. It appears that while the ranges are /30 someone is trying to brute-force the network and/or broadcast addresses for the ranges. When I change them to be a /29, now the router sees the traffic and starts dropping packets. Are there any suggestions for mitigating this behavior or is it just the nature of the beast?
-- 101010
No nothing like that. I'm just removing the .0/30 and 4/30 subnets and adding .0/29. To your previous question, yes .0 and .3 are unused. Once I change the subnet .3 becomes a usable IP and it's getting hammered with traffic, causing packet loss. On 6/25/19 3:30 PM, Mel Beckman wrote:
Also, what do you mean by “join to /30 public subnets to a /29”? You can’t overlap subnets, if that’s what you’re thinking.
-mel
On Jun 25, 2019, at 3:27 PM, Mel Beckman <mel@beckman.org> wrote:
You’re using just the two middle IPs in the four that make up the /30 set, right? IOW, the subnet x.x.x.0/30 should have .0 and .3 unused (they’re broadcast), and you use .1 and .2.
-mel
On Jun 25, 2019, at 9:41 AM, Scott <scott@viviotech.net> wrote:
First, sorry if this is a bit of a noob question.
I'm trying to find a way of preventing a slew of traffic to an IP, or IP's, when I join two /30 public subnets to a /29. It appears that while the ranges are /30 someone is trying to brute-force the network and/or broadcast addresses for the ranges. When I change them to be a /29, now the router sees the traffic and starts dropping packets. Are there any suggestions for mitigating this behavior or is it just the nature of the beast?
-- 101010
-- 101010
If the sources are from many different IPs, it could be a DDoS attack that you simply didn’t notice before. You can black-hole individual IPs using a /32 null0 route. That will at least stop your border router from trying to ARP the destination, reducing broadcast traffic on the subnet. In fact, it’s a good idea to configure /32 null0 routes for IPs you don’t use. Those IPs can’t then be scanned. -mel
On Jun 25, 2019, at 3:50 PM, Scott <scott@viviotech.net> wrote:
No nothing like that. I'm just removing the .0/30 and 4/30 subnets and adding .0/29.
To your previous question, yes .0 and .3 are unused. Once I change the subnet .3 becomes a usable IP and it's getting hammered with traffic, causing packet loss.
On 6/25/19 3:30 PM, Mel Beckman wrote:
Also, what do you mean by “join to /30 public subnets to a /29”? You can’t overlap subnets, if that’s what you’re thinking.
-mel
On Jun 25, 2019, at 3:27 PM, Mel Beckman <mel@beckman.org> wrote:
You’re using just the two middle IPs in the four that make up the /30 set, right? IOW, the subnet x.x.x.0/30 should have .0 and .3 unused (they’re broadcast), and you use .1 and .2.
-mel
On Jun 25, 2019, at 9:41 AM, Scott <scott@viviotech.net> wrote:
First, sorry if this is a bit of a noob question.
I'm trying to find a way of preventing a slew of traffic to an IP, or IP's, when I join two /30 public subnets to a /29. It appears that while the ranges are /30 someone is trying to brute-force the network and/or broadcast addresses for the ranges. When I change them to be a /29, now the router sees the traffic and starts dropping packets. Are there any suggestions for mitigating this behavior or is it just the nature of the beast?
-- 101010
-- 101010
Scott wrote : No nothing like that. I'm just removing the .0/30 and 4/30 subnets and adding .0/29. To your previous question, yes .0 and .3 are unused. Once I change the subnet .3 becomes a usable IP and it's getting hammered with traffic, causing packet loss.
You change the subnet mask on both sides, right ? Looks to me like expected behavior. On the sending router, with a /30 mask the .3 address is not usable, so the sending router does not send traffic. When you change to the /29 mask, .3 becomes usable, the sending router ARPs it, and starts sending traffic. In a way, that is possibly good news, as it allows you do find out that you may have a DOS or a DDOS attack going on your .3 address. Michel. On 6/25/19 3:30 PM, Mel Beckman wrote:
Also, what do you mean by “join to /30 public subnets to a /29”? You can’t overlap subnets, if that’s what you’re thinking.
-mel
On Jun 25, 2019, at 3:27 PM, Mel Beckman <mel@beckman.org> wrote:
You’re using just the two middle IPs in the four that make up the /30 set, right? IOW, the subnet x.x.x.0/30 should have .0 and .3 unused (they’re broadcast), and you use .1 and .2.
-mel
On Jun 25, 2019, at 9:41 AM, Scott <scott@viviotech.net> wrote:
First, sorry if this is a bit of a noob question.
I'm trying to find a way of preventing a slew of traffic to an IP, or IP's, when I join two /30 public subnets to a /29. It appears that while the ranges are /30 someone is trying to brute-force the network and/or broadcast addresses for the ranges. When I change them to be a /29, now the router sees the traffic and starts dropping packets. Are there any suggestions for mitigating this behavior or is it just the nature of the beast?
-- 101010
-- 101010
TSI Disclaimer: This message and any files or text attached to it are intended only for the recipients named above and contain information that may be confidential or privileged. If you are not the intended recipient, you must not forward, copy, use or otherwise disclose this communication or the information contained herein. In the event you have received this message in error, please notify the sender immediately by replying to this message, and then delete all copies of it from your system. Thank you!...
Michel is right. This is a common configuration error: failing to have the mask agree on all interfaces. This is indeed what you would see. -mel On Jun 25, 2019, at 4:07 PM, Michel Py <michel.py@tsisemi.com<mailto:michel.py@tsisemi.com>> wrote:
Scott wrote : No nothing like that. I'm just removing the .0/30 and 4/30 subnets and adding .0/29. To your previous question, yes .0 and .3 are unused. Once I change the subnet .3 becomes a usable IP and it's getting hammered with traffic, causing packet loss.
You change the subnet mask on both sides, right ? Looks to me like expected behavior. On the sending router, with a /30 mask the .3 address is not usable, so the sending router does not send traffic. When you change to the /29 mask, .3 becomes usable, the sending router ARPs it, and starts sending traffic. In a way, that is possibly good news, as it allows you do find out that you may have a DOS or a DDOS attack going on your .3 address. Michel. On 6/25/19 3:30 PM, Mel Beckman wrote:
Also, what do you mean by “join to /30 public subnets to a /29”? You can’t overlap subnets, if that’s what you’re thinking.
-mel
On Jun 25, 2019, at 3:27 PM, Mel Beckman <mel@beckman.org<mailto:mel@beckman.org>> wrote:
You’re using just the two middle IPs in the four that make up the /30 set, right? IOW, the subnet x.x.x.0/30 should have .0 and .3 unused (they’re broadcast), and you use .1 and .2.
-mel
On Jun 25, 2019, at 9:41 AM, Scott <scott@viviotech.net<mailto:scott@viviotech.net>> wrote:
First, sorry if this is a bit of a noob question.
I'm trying to find a way of preventing a slew of traffic to an IP, or IP's, when I join two /30 public subnets to a /29. It appears that while the ranges are /30 someone is trying to brute-force the network and/or broadcast addresses for the ranges. When I change them to be a /29, now the router sees the traffic and starts dropping packets. Are there any suggestions for mitigating this behavior or is it just the nature of the beast?
-- 101010
-- 101010
TSI Disclaimer: This message and any files or text attached to it are intended only for the recipients named above and contain information that may be confidential or privileged. If you are not the intended recipient, you must not forward, copy, use or otherwise disclose this communication or the information contained herein. In the event you have received this message in error, please notify the sender immediately by replying to this message, and then delete all copies of it from your system. Thank you!...
participants (3)
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Mel Beckman -
Michel Py -
Scott