Juniper ARP Policer on PTX
I’ve written before about the default ARP policer on Juniper MX. It can create some odd failure conditions when you’re connected to noisy networks such as large Internet Exchanges. Junos OS Evolved, as used on platforms like the PTX10003 has low default values for ARP and ICMPv6 ND DDoS protections. It will cause the same problems, but is easier to diagnose and mitigate.
Juniper DDoS Protection
Platforms like MX, QFX, PTX have Control Plane DDoS protections built in. These will automatically rate-limit various traffic types that hit the CPU. This is generally a Good Thing. Certain packet types get punted from the ASIC to the CPU, but the CPU can’t handle anywhere near the traffic levels that the forwarding ASIC can. Send enough special packets to a router, choke the CPU, and you might be able to knock things offline. So having default policies to rate-limit traffic makes sense.
Platform Defaults
Juniper might have “One Junos” but we know it’s not that simple. Behavior varies between platforms. Check these default values for some DDoS protections for different platforms:
| Protocol | MX | QFX | PTX |
|---|---|---|---|
| ARP | 20,000 | 500 | 500 |
| NDPv6 | 20,000 | N/A | 500 |
| ICMP | 20,000 | N/A | 500 |
| BGP | 20,000 | 3,000 | 5,000 |
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