Paste a configuration to check it for internal contradictions: duplicate addresses, overlapping subnets, undeclared VLANs, unreachable ACL rules, DHCP overlap and unreachable next hops. Runs entirely in the browser — nothing is uploaded.
Parsed as core-01
ACL GUEST_IN is applied but not defined
Vlan10 references GUEST_IN in, but no such ACL exists in this configuration. Behaviour depends on platform — many deny all traffic.
interface Vlan10Duplicate IP address 10.0.10.1
Configured on both Vlan10 (line 6) and Vlan20. One of the two interfaces will fail to come up.
10.0.10.1Overlapping subnets on different interfaces
Vlan10 (10.0.10.0/24) overlaps Vlan20 (10.0.10.0/24). Routing between them is ambiguous.
interface Vlan20VLAN 20 is used but never declared
Referenced by Vlan20 but there is no "vlan 20" statement. On most platforms the VLAN will not be created and traffic will be dropped.
interface Vlan20Vlan30 is assigned the broadcast address
10.0.30.255/24 is the broadcast address of its own subnet.
interface Vlan30VLAN 30 is used but never declared
Referenced by Vlan30 but there is no "vlan 30" statement. On most platforms the VLAN will not be created and traffic will be dropped.
interface Vlan30VLAN 99 is used but never declared
Referenced by GigabitEthernet0/1 but there is no "vlan 99" statement. On most platforms the VLAN will not be created and traffic will be dropped.
interface GigabitEthernet0/1Overlapping DHCP scopes
Pool "USERS" (10.0.10.0/24) overlaps "OVERLAP" (10.0.10.0/23). The same address can be handed to two clients.
ip dhcp pool OVERLAPInterfaces have differing MTUs
Found 9000, 1500. Mismatched MTU prevents OSPF adjacency forming and black-holes large packets where PMTUD is broken.
ACL UNUSED_LIST is defined but never applied
No interface references this ACL, so it has no effect. Either apply it or remove it — an unapplied ACL reads as protection that is not there.
ip access-list extended UNUSED_LISTACL UNUSED_LIST permits all traffic before later rules
Line 27 matches everything, so the 1 rule(s) after it can never be reached.
permit ip any anyNext hop 172.16.99.1 is not on a connected subnet
The route to 192.168.0.0/16 points at a gateway that no configured interface can reach directly. The route will not install unless it is recursive.
ip route 192.168.0.0 255.255.0.0 172.16.99.1Credential stored in plaintext
This value is readable by anyone with access to the config or a backup of it. Use an encrypted form, and keep the config out of version control if it must stay.
username admin password ********Vlan10 has no description
Undescribed interfaces make outage triage slower than it needs to be.
interface Vlan10Vlan30 has no description
Undescribed interfaces make outage triage slower than it needs to be.
interface Vlan30GigabitEthernet0/1 has no description
Undescribed interfaces make outage triage slower than it needs to be.
interface GigabitEthernet0/1GigabitEthernet0/2 has no description
Undescribed interfaces make outage triage slower than it needs to be.
interface GigabitEthernet0/2